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1
Rätsch, Christian. « Effects of strain on heteroepitaxial growth dynamics ». Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/30647.
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Meng, Shuang. « Heteroepitaxial growth of gallium selenium compounds on silicon / ». Thesis, Connect to this title online ; UW restricted, 2000. http://hdl.handle.net/1773/9749.
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BERGAMASCHINI, ROBERTO. « Continuum models of heteroepitaxial growth on patterned substrates ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2013. http://hdl.handle.net/10281/40087.
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The continuous advancing of semiconductor technologies in micro-electronics,
optics, energy production, ..., constantly demands for an improvement in the
choice of suitable materials. Heteroepitaxial systems represents a class of materials
that has been largely exploited to achieve such enhancements thanks to the
possibility to combine properties of the different material with a large degree of
customization and tuning. Many different heteroepitaxial systems are possible, from small nanostruc-
tures (e.g. quantum dots, islands), to microscopic crystals or films. Generally
such structures form spontaneously during the growth in consequence of a self-
assembly process. If the growth is operated on flat undifferentiated substrate
the self-assembly process can be controlled only on a rather limited extent, by
properly tuning the growth conditions responsible for the material rearrangement
during the growth. The possibility to achieve a major control on the
formation of the different structures along the surface is highly desirable.
Substrate patterning techniques strongly evolved in the last decade allowing for a
better control of the system evolution through the introduction of preferential
sites where the growing material can accumulate and evolve in a more controllable
way. With this respect, the understanding of the mechanisms underlying
the specific growth modes observed experimentally is crucial to proficiently define
the optimal growth conditions for the desired behavior. Growth models
for heteroepitaxial systems are then widely used on very different scales. Due
to the large variability of the systems, different models need to be in general
considered for the several typologies of materials and growth methods.
In this Thesis we essentially focus our attention on two different physical
systems: the Stranski-Krastanow growth of three-dimensional islands on pit-
patterned substrates, and the growth of 3D crystals on substrate patterned with
pillar structures, on the micrometer size scale. In order to define the appropriate
way of modeling, the characteristic size and time scale of the systems should be
taken into account. The typical periodicity of patterns used for island growth
in Stranski-Krastanow pit is larger than 100 nm and the grown islands can in
general become very large, including several milions of atoms. Deposition of
few atomic layers are usually considered but the growth rate is typically slow
so that the growth process lasts for minutes. The growth on pillar patterns
is performed on even larger size scale, with typical dimensions of μm; also,
several μm of material are deposited so that the growth can even require hours.
Evidently, an atomistic description is not feasible so that a coarsened scale must
be considered. Continuum models are hence the best choice for the description
of these kind of systems, as they allow to efficiently describe the overall profile
evolution for long time scales, including most of the physics resulting from the
underlying atomic events in an average way.
The problem of Stranski-Krastanow island growth can be mainly defined
on the basis of thermodynamic arguments as it is typically obtained by slow
Molecular Beam Epitaxy at temperature high enough to guarantee an effective
diffusion dynamics of the atoms along the surface. Such conditions can be
considered close enough to equilibrium so that the main driving force for the system
evolution is the free energy minimization, although, as largely discussed in this
work, thermodynamics applies only to the surface region. Thermodynamic-
driven profile evolution has been object of large interest since the seminal work
by W.W. Mullins, more than fifty years ago. Several models accounting for the
effects of surface energy and profile faceting have been developed. Strain effects
have also been successfully included, offering a deeper insight on the islanding
mechanisms in connection with the raise of morphological instability of a flat
film. Several studies have been devoted also to the characterization of the role
of substrate patterning. However, most of these models were based on a single
component picture loosing a crucial element that proved to play an essential
role in the evolution of the growth process: intermixing between the deposited
material and the substrate one. Some attempts to account for this effect,
accounting for the evolution of the composition profile have been proposed. In
2003, J. Tersoff developed a successful description of the coupled evolution of
profile and composition, based on the restriction of intermixing within a small
layer around the surface, that proved to be particularly well suited to capture the
main physics of Stranski-Krastanow heteroepitaxial growth on flat substrate.
In this Thesis we discuss of an extension of the original Tersoff model to the
characterization of the growth on pit-patterned substrate, developed in direct
collaboration with J. Tersoff himself. Ge/Si system is considered. In particular,
a realistic description of the surface dynamics for the adatoms of both
components, accounting for their different mobilities and its dependence on the
local environment, is introduced into the model derivation. Simulations are
then implemented for an initial pit-patterned geometry of the substrate and the
evolution is investigated in comparison with the experimental phenomenology.
An effect of anomalous smoothing of the substrate profile induced in the initial
stages of the growth and recently observed in experiments is analyzed in details
and explained on the basis of simulation results. Islands formation is also
inspected and their morphological evolution is considered.
Tersoff approach was proved to be effective to capture the main physical as-
pects related to the intermixing dynamics, crucial for the understanding of many
aspects of heteroepitaxy. Some technical limitations however reduce the
possibilities to extend it to complex system geometries, in particular three-dimensional
systems. In order to allow for a future study of more general problems,
during this Thesis work an original phase-field model for heteroepitaxial growth
has been developed, in collaboration with A. Voigt and his group. Phase-field
technique was found to be particularly well suited for the analysis of surface
processes, offering an efficient way to represent the profile evolution of a free
surface upon surface diffusion, eventually including also strain effects. Multiple
component systems are also considered in phase-field models for alloy
solidification. An exhaustive model for the heteroepitaxial processes, including both
surface dynamics and intermixing effects, is not yet available in literature. The
purpose of this part of the Thesis then consists in the definition of a suitable
model accounting for such peculiar features of Stranski-Krastanow heteroepitaxial
systems. A proof of concepts is provided by example simulations, testing
the effects of the various contribution defining the problem.
The modeling of the growth processes leading to the self-assembly of
crystals on pillar patterned substrates is much different as the growth in this case
is obtained in conditions of high growth rates and relatively low temperature,
driving the system well far from equilibrium, in conditions such that the
thermodynamic driving forces are frustrated by kinetic effects. In this case, a different
approach is needed, properly accounting for the different kinetics at the surface.
In particular, a modeling for such conditions can be defined by exploiting the
local mechanisms of atomic exchange between the grow flux and the advancing
crystal front by means of suitable rate equations. The dynamics on the
different facets of crystals is then characterized in terms of an orientation
dependent growth rate, mainly determined by the impinging flux. In this Thesis a
model including both intrinsic different growth properties and local deposition
fluxes is defined and used to interpret the growth of micrometric 3D crystals
on a suitable pattern of pillars, obtained in experiments for both Ge/Si and
GaAs/Si pillars. Simulation results allow to inspect the key features of the
observed growth modality, showing the crucial role of frustrated diffusion and
mutual flux shielding between neighboring crystals. A close comparison with
the experiments is reported.
4
Mao, Jun. « Heteroepitaxial growth on silicon surface : a Monte Carlo study ». Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30582.
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The purpose of this thesis is to investigate the initial stages of the growth of heteroepitaxial films on Si substrates. Two prototype systems were chosen for this research: first is Ge/Si(001), where the two species have similar chemical properties; second is CaF2/Si(111), in which the ionic epitaxial film and substrate have similar crystal structures. Both are strained heteroepitaxial films because of their lattice mismatch. These systems have attracted much attention largely due to various promising applications in micro-electronics and fundamental interest in the basic studies of heteroepitaxy. The Metropolis Monte Carlo method is used for this research. For Ge/Si, because of short range interaction forces between atoms, the CELL method is developed and applied to this research. Results have shown that the such a method is fast, efficient and is easily adapted to study all other systems with short range interaction forces; the other method, called the BIG JUMP, is also developed. The results have shown that the BIG JUMP method is particularly useful in generating equilibrium or metastable configurations. The initial stage of MBE growth of Ge on Si(001) was studied using MC method combined with CELL method, or both CELL and BIG JUMP methods. It was found that at least an (8 x 8 x 8) computational cell with six layers that were allowed to move was needed for the simulations. 2% acceptance of MC moves was found to lead a quicker energy minimisation process. This result implies that the energy minimisation process involves big jumps of atoms, corresponding to atom diffusion on a real surface. The energy map of a Ge atom on Si(001)(2 x 1) was calculated and compared with ab initio calculation. An exchange mechanism of a Ge adatom with a Si atom of the substrate was found. This mechanism can be used in understanding the ordered structure observed during the initial stage of MBE growth of Ge on a Si(001) substrate surface.
5
Wallace, Julia M. « Growth and characterisation of heteroepitaxial ZnSe and ZnSxSe1-x ». Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/806.
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Hatfield, Stuart Andrew. « Heteroepitaxial growth of MnSb on III-V semiconductor substrates ». Thesis, University of Warwick, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444834.
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吳誼暉 et Yee-fai Ng. « Heteroepitaxial growth of InN on GaN by molecular beam epitaxy ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B29797846.
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Ng, Yee-fai. « Heteroepitaxial growth of InN on GaN by molecular beam epitaxy / ». Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25212175.
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Xu, Zhehan. « Direct Heteroepitaxial Growth of III-Vs on Si by HVPE ». Thesis, KTH, Tillämpad fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-265624.
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McIntyre, Paul Cameron. « Heteroepitaxial growth of chemically derived Ba₂YCu₃O₇âx thin films ». Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12741.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1993.Includes bibliographical references (leaves 168-177).
by Paul Cameron McIntyre.
Sc.D.
11
Reyes-Natal, Meralys. « Modeling and growth of the 3C-SiC heteroepitaxial system via chloride chemistry ». [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002691.
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Röder, Holger. « Microscopic processes in heteroepitaxial growth : nucleation, growth and alloying of silver on the (111) surface of platinium / ». [S.l.] : [s.n.], 1994. http://library.epfl.ch/theses/?nr=1288.
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GATTI, RICCARDO. « Modeling elastic and plastic relaxation in silicon-germanium heteroepitaxial nanostructures ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/18965.
Texte intégralRésumé :
My Ph. D. work led to the development of numerical methods devoted to the study of elastic and plastic relaxation in SiGe/Si (001) heteroepitaxial nanostructures. The meth- ods were successfully applied to the study of self-assembled nanostructures arising from the heteroepitaxial growth of Ge (or SiGe alloys) on Si substrate (three dimensional islands and thin films). First of all, I studied the mechanisms allowing for elastic relaxation. Tuning the initial condition, it was possible to calculate with Finite Element Method the elas- tic field in SiGe islands. Then the variation of compositional profile, observed during the three dimensional growth, were determined by an ad hoc Monte Carlo algorithm coupled with FEM. My main contributions, however, were in the field of plastic relaxation and the study of dislocations in nanostructures. First I developed a novel approach to handle misfit dislocation in nanostructures in the FEM framework. The developed method allows for determining the elastic field of dislocations in small size object, where the extended defects deeply interact with free surfaces and interfaces. It was shown how my novel computational strategy can be applied to the study of the plastic relaxation onset (introduction of the first dislocations) in Ge/Si islands, finding an excellent agreement with experimental data. Fur- thermore we depicted how by proper patterning of the Si (001) substrate it is possible to predict dislocation confinement, as confirmed experimentally by AFM and TEM analysis, in prescribed areas of the heteroepitaxial system, opening a viable path for dislocation en- gineering. Then, I adapted the microMegas dislocation dynamics (DD) code to dislocation propagation in nanostructures. The DD code was originally designed to study the time evolution of extended defects in bulk system. I therefore introduced suitable modifications for treating free surfaces and for handling the propagation of threading arms (dislocation touching free surfaces) in the system. Simulations performed in overgrown islands, predict a dislocation pattern at the SiGe island extremely similar to the experimentally observed dislocation microstructure.
14
ALBANI, MARCO GIOCONDO. « Modeling of 3D heteroepitaxial structures by continuum approaches ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241273.
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I semiconduttori sono una categoria di materiali fondamentali per lo sviluppo di molteplici dispositivi. Negli ultimi decenni, l’evoluzione dell’industria dei semiconduttori ha seguito la nota legge di Moore. Tuttavia, questo straordinario processo di innovazione va incontro a un ostacolo nei prossimi anni, in quanto il processo di miniaturizzazione sta raggiungendo la scala atomica. Per questo motivo, è necessario sviluppare strategie alternative. In particolare, metodi di crescita bottom-up sono attualmente studiati per lo sviluppo di nanostrutture 3D.
In questa Tesi, per riprodurre la dinamica di crescita 3D, abbiamo sviluppato una tecnica modellistica che possa trattare la crescita verticale di nanostrutture. Un approccio cinetico, legato alla dinamica di incorporazione degli adatomi, deve essere utilizzato per simulare questo regime di crescita, che non può essere correttamente spiegato con un approccio termodinamico standard, basato sulle densità di energia superficiale. La simulazione di crescite verticali è un risultato complicato non solo per la definizione di un modello appropriato, ma richiede anche una tecnica numerica specifica. In particolare, in questa Tesi, abbiamo adottato un modello phase-field applicato allo studio della crescita di nanomembrane di GaAs, sfruttando il metodo a elementi finiti per la risoluzione numerica delle equazioni di evoluzione del sistema.
Per lo sviluppo di dispositivi, è spesso necessario ricorrere a etero-strutture, che combinano diversi tipi di semiconduttori, per esempio per le applicazioni optoelettroniche dove spesso si utilizzano delle giunzioni p-n. Inoltre, la crescita eteroepitassiale può essere sfruttata anche per trasferire la struttura cristallina da un materiale a un altro. In questa Tesi, ci siamo focalizzati sullo studio di nanofili core/shell e abbiamo effettuato un’accurata caratterizzazione delle deformazioni elastiche della struttura cristallina che si verificano in questi sistemi. In particolare, il rilassamento elastico è stato studiato con un modello continuo, basato sul metodo a elementi finiti. In particolare, abbiamo studiato il fenomeno di piegamento di nanowire GaP/InGaP e abbiamo correlato questo fenomeno con la distribuzione delle deformazioni elastiche all’interno della struttura. Inoltre, abbiamo investigato il ruolo del rilassamento elastico nei nanofili Ge/GeSn in riferimento al fenomeno di incorporazione di Sn nella shell.
L’evoluzione di nanostrutture può essere determinata anche dall’effetto combinato di energia di superficie ed energia elastica. L’esempio più studiato in letteratura è la crescita eteroepitassiale di isole su substrati planari, secondo la modalità di crescita di tipo Stranski-Krastanov. Per le applicazioni tecnologiche, è fondamentale poter controllare la distribuzione spaziale e l’uniformità della taglia delle isole.
In questa Tesi, presentiamo un modello di crescita phase-field, che combina la descrizione della dinamica di diffusione superficiale con la caratterizzazione tramite elementi finiti del rilassamento elastico, al fine di simulare la crescita ordinata di isole su substrati patternati con pit. In particolare, ci focalizziamo sul sistema prototipico di Ge cresciuto su Si. Il vantaggio del modello phase-field basato sul metodo a elementi finiti è la possibilità di risolvere in modo esatto le equazioni di evoluzione, senza la necessità di adottare approssimazioni di ordine superiore nella formulazione delle equazioni, pur considerando con precisione la geometria patternata del substrato.Semiconductors are the main building block for a variety of devices in our life. The semiconductor industry, in the last decades, has evolved by following the Moore's law. However, this incredible innovation process is going to reach an end in the next years, as the miniaturization process is getting too close to the atomistic size, which hinders the development of smaller devices. Therefore, alternative ways to evolve the current technologies have to been exploited. In particular, bottom-up approaches are currently being studied for the growth of 3D nanostructures. In this Thesis, to deal with the 3D growth dynamics, we develop a modeling technique that can reproduce the vertical growth of nanostrucutures. A kinetic approach, related to the incorporation dynamics of adatoms on the surface, has to be adopted to model the peculiar growth of 3D nanostructures, which cannot be explained by the standard thermodynamic arguments based on the surface energy densities. The simulation of the vertical growth is not just challenging for the definition of a proper model, but it requires also a dedicated technique for the numerical solution of the evolution dynamics. In particular, in this Thesis, we exploit a phase field model to simulate the growth on GaAs nanomembranes, based on a finite element method for the solution of the evolution equations. For the development of devices, it is often required to build heterostructures which combine different semiconductors, for instance for optoelectronic applications where a p-n junction is required. Furthermore, the heteroepitaxial growth can be exploited also to transfer some structural material properties, such as the hexagonal lattice structure, from a material to another. In this Thesis, we focus on the core/shell nanowire heteroepitaxial system and we provide a detailed characterization of the elastic deformations in the crystal structure. The elastic relaxation is studied in a continuum elasticity framework by finite element method. In particular, we study the bending of GaP/InGaP nanowires and we correlate this phenomenon with the partitioning of the elastic deformation within the nanostructure. Moreover, we investigate the role of the elastic relaxation in Ge/GeSn core/shell nanowires with respect to the incorporation of Sn in the shell. The evolution of nanostructures can be driven also by the combined effect of surface energy and elastic energy contributions. One of the most studied examples of this is the heteroepitaxial growth of islands on planar substrates, following the Stranski-Krastanov growth mode. For technological applications it is fundamental to control the spatial distribution and the size-uniformity of the islands. In this Thesis, we propose a phase-field model which combines the description for the surface diffusion dynamics and the finite element characterization of the strain field to study the ordered growth of islands on pit-patterned substrates. In particular, we choose the prototypical system where Ge islands are grown on a Si substrate. The advantage of the phase-field model based on finite element method is the possibility to exactly solve the evolution equations of the system, without the need of higher order approximations and with the possibility to precisely consider the effect on the elastic relaxation which is provided by the substrate morphology.
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Liu, Ying. « Heteroepitaxial growth of InN and InGaN alloys on GaN(0001) by molecular beam epitaxy ». Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36363558.
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Liu, Ying, et 劉穎. « Heteroepitaxial growth of InN and InGaN alloys on GaN(0001) by molecular beam epitaxy ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36363558.
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Piquette, Eric C. McGill T. C. « Molecular beam heteroepitaxial growth and characterization of wide band gap semiconductor films and devices / ». Diss., Pasadena, Calif. : California Institute of Technology, 1999. http://resolver.caltech.edu/CaltechETD:etd-11292006-152956.
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Jang, Syun-Ming. « Growth, characterization and thermal stability of undoped and in-situ doped silicon-germanium heteroepitaxial layers ». Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12744.
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Niu, Xiaobin. « Level-set simulations of self-assembled nano patterns and stacked quantum dots during heteroepitaxial growth ». Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1610041041&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Zabaleta, Llorens Jone. « Growth and advanced characterization of solution-derived nanoscale La Sr MnO heteroepitaxial 0.7 0.3 3 systems ». Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/294276.
Texte intégralRésumé :
Este trabajo trata del crecimiento y de la caracterización de sistemas heteroepitax¬iales ferromagnéticos de manganita La0.7Sr0.3MnO3 (LSMO). El LSMO es un oxido complejo que exhibe fenómenos tales como la magnetorresistencia colosal y la semi-metalicidad, lo que lo convierten en firme candidato para aplicaciones tecnológicas como sensores y memorias magnéticas. Muchas de estas aplicaciones requieren la miniaturización del LSMO a rangos nanométricos con bajo coste. Esta miniaturización, además, conlleva la aparición de fenómenos nuevos e interesantes, consecuencia de las nuevas relaciones que, en la nanoescala, se establecen entre los átomos constituyentes.
En esta tesis demostramos la generación de LSMO epitaxial y ferromagnético en forma de capas 2D ultra delgadas (con grosores inferiores a 10 nm) y de nanoislas 3D autoensambladas (con diámetros inferiores a 200 nm, grosores inferiores a 40 nm) mediante un método químico escalable basado en el empleo de soluciones ultradilu¬idas. El crecimiento 2D o 3D del LSMO lo determina la elección del monocristal óxido sobre el que crece la manganita. Esto a su vez subraya el rol determinante que tienen, en el marco del crecimiento heteroepitaxial, el desacoplo entre redes cristalográficas y las energías de superficie e intercara. Se trata aquí la morfología, la estructura cristalina y el estado de deformación de las capas ultra delgadas y de las nanoislas autoensambladas. Las medidas magnéticas macroscópicas muestran que las temper-aturas de Curie de capas e islas (Tc~350 K) son comparables al valor de Tc reportado en la literatura para LSMO masivo. Estos resultados contrastan con la tendencia gen-eral observada en la literatura para capas ultra delgadas depositadas por métodos vía vapor y para islas litografiadas, tendencia según la cual la Tc muestra valores significativamente inferiores a 350 K. Las medidas preliminares de transporte realizadas en las capas de LSMO de esta tesis revelan, adicionalmente, el desacoplo de las transiciones ferromagnética-paramagnética y metal-aislante, además de un incremento sustancial de la magnetorresistencia.
El sistema de nanoislas 3D ferromagnéticas autoensambladas de LSMO se ha anal-izado en mayor profundidad empleando técnicas de caracterización local, con el objeto de descubrir sus propiedades funcionales. El estudio detallado mediante micoscopía de fuerzas magnéticas (MFM) muestra la correlación entre la estructura magnética y las características geométricas de las nanoislas de LSMO, donde el estado de vórtice juega un rol central. También hemos abordado el reto que suponen islas tan pequeñas (inferiores a 200 nm en tamaño lateral) crecidas sobre sustratos aislantes en su estudio mediante Microscopía de fotoemisión de electrones (PEEM) y Microscopía Kelvin de fuerzas (KPFM). La investigación por PEEM nos ha provisto de información este¬quiométrica de las islas y ha mostrado el comportamiento magnético de algunas de las más grandes. Por su parte, mediante KPFM se ha observado la anisotropía de la función trabajo entre las facetas de las nanoislas de LSMO, lo que abre el camino a la caracterización electrostática de la superficie de óxidos complejos nanométricos.This work deals with the growth and the comprehensive characterization of nanoscale ferromagnetic La0.7Sr0.3MnO3 (LSMO) manganite heteroepitaxial systems. LSMO is a complex oxide exhibiting phenomena such as Colossal magnetoresistance and half metallicity, and, thus, an appealing candidate for potential technological applications like magnetic sensors and memories. Many of these applications require the down-scaling of LSMO to the nanometer range, and to do so cost-effectively. Moreover, such miniaturization raises novel and interesting phenomena, consequence of the new relationships that are established between the constituent atoms at the nanoscale. In this thesis we demonstrate that a scalable, bottom-up approach based on ultra-diluted chemical solutions succeeds in generating high quality ferromagnetic epitaxial LSMO ultra-thin films (2D) (below 10 nm in thickness) and self-assembled nanoislands (3D) (diameters below 200 nm, thicknesses below 40 nm). Whether the system arranges into a 2D or a 3D configuration is determined by the choice of the single crystal oxide substrate underneath, which highlights the key role of lattice mismatch and of surface/interface energies in heteroepitaxial growth. We address here the morphology, crystal structure, and strain state of ultra-thin films and self-assembled nanoislands. Macroscopic magnetic characterization reveals that the measured Curie temperatures (Tc~350 K) are comparable to the Tc value reported for bulk LSMO. This is a remarkable fact in LSMO ultra-thin films and sub-200 nm nanoislands, given the experimental tendency, for vapor-deposited LSMO thin films and lithographied nanoislands, to show depressed Tc values. Preliminary transport measurements in the LSMO films also display interesting features, such as the decoupling of the metal-insulator and the ferromagnetic-paramagnetic transitions and an enhanced magnetoresistance. The system of ferromagnetic self-assembled 3D nanoislands is further explored by means of local characterization techniques, in order to unveil their local functional properties. Detailed Magnetic Force Microscopy investigations show the correlation between the magnetic structure and the geometrical characteristics of the LSMO nanoislands, with the vortex-state playing a central role. The challenges of Photoemission electron microscopy (PEEM) and Kelvin Probe Microscopy (KPFM) measurements in these sub-200 nm LSMO nanoislands, grown on insulating substrates, are also addressed. PEEM provides information on the stoichiometric composition and on the magnetic structure of some of the largest nanoislands. KPFM, in turn, shows a local work function anisotropy between the facets of the LSMO nanoislands, and opens the path to the electrostatic characterization of nanoscale complex oxides.
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Onojima, Norio. « Heteroepitaxial Growth of High-Quality AIN on SiC by Molecular-Beam Epitaxy toward Electronic Device Application ». 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/77767.
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Da, Conceicao Lorenzzi Jean Carlos. « Growth and doping of heteroepitaxial 3C-SiC layers on α-SiC substrates using Vapour-Liquid-Solid mechanism ». Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10179.
Texte intégralRésumé :
L'utilisation récente d'une voie originale de croissance cristalline basée sur les mécanismes vapeur-liquide-solide (VLS) à partir d'un bain Ge-Si a permis des améliorations importantes de la qualité cristalline des couches minces hétéroépitaxiales de SiC-3C sur substrats sur substrat α-SiC(0001). Ce travail a pour but d'approfondir les connaissances sur cette technique de croissance, d'améliorer le procédé et de déterminer les propriétés du matériau élaboré. La première partie est dédiée à la compréhension et la maîtrise des différents mécanismes impliqués dans la croissance de SiC-3C par VLS. Cela a notamment permis la détermination des paramètres limitant la taille des échantillons et la démonstration des avantages à utiliser des alliages fondus contant 50 at% de Ge au lieu de 75 at%. Une étude de la croissance latérale sur substrats patternés a donné des indications intéressantes pouvant être intégrées dans le modèle d'élimination des macles. L'incorporation intentionnelle et non intentionnelle de dopants de type n et p pendant la croissance VLS a été suivie. Pour le dopage n, nous avons démontré l'existence d'un lien clair entre l'impureté N et la stabilisation du polytype SiC-3C. En outre, nous avons réussi à abaisser le dopage résiduel n des couches en dessous de 1x1017 cm-3. Pour le dopage p, le meilleur élément n'est pas le Ga mais l'Al, même s'il doit être ajouté à un alliage de type Si-Ge pour éviter l'homoépitaxie. Enfin, ces couches ont été caractérisées optiquement et électriquement par différentes techniques. Les mesures C-V et G-V ont permis d'estimer une concentration très faible (7×109 cm-2) de charges fixes dans l'oxyde SiO2 ainsi qu'une densité d'états d'interface aussi basse que 1.2×1010 cm-2eV-1 à 0.63 eV sous la bande de conduction. Ces valeurs record sont une très bonne base pour le développement d'un composant de type MOSFET en SiC-3CRecently, the use of an original growth approach based on vapour-liquid-solid (VLS) mechanism with Ge-Si melts has led to significant improvement of the crystalline quality of the 3C-SiC thin layers heteroepitaxially grown on α-SiC(0001) substrate. This work tries to deepen the knowledge of such specific growth method, to improve the process and to determine the properties of the grown material. The first part was dedicated to the understanding and mastering of the various mechanisms involved in 3C-SiC growth by VLS mechanism. This led to the determination of the parameters limiting sample size and the demonstration of the benefits of using 50 at% Ge instead of 75 at% Ge melts. A study of lateral enlargement on patterned substrates gave some interesting hints which can be integrated in the model of twin defect elimination. The incorporation of non intentional and intentional n- and p-type dopants during VLS growth was studied. For n-type doping, a clear link between N impurity and 3C polytype stability was demonstrated. Besides, high purity layers with residual n-type doping below 1x1017 cm-3 were achieved. For p-type doping, the best element was shown to be Al and not Ga, even if it has to be alloyed with Ge-Si melts to avoid homoepitaxial growth. Finally, these layers were characterised by several optical and electrical means like Raman spectroscopy, low temperature photoluminescence, deep leveltransient spectroscopy and MOS capacitors measurements. Very low concentrationsof fixed oxide charges estimated about 7×109 cm-2 and interface states densities Dit equal to 1.2×1010 cm-2eV-1at 0.63 eV below the conduction band have been achieved. These record values are a very good base toward 3C-SiC MOSFET
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Nakamura, Kazuhiro. « Heteroepitaxial Growth of InGaP and GaAsP on Si and Their Doping Characteristics for the Application to Tandem Solar Cells ». Kyoto University, 2001. http://hdl.handle.net/2433/150652.
Texte intégral
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Heilmann, Martin Verfasser], et Gerd [Gutachter] [Leuchs. « Heteroepitaxial Growth of GaN Nanostructures via Metalorganic Vapor Phase Epitaxy on Sapphire and Silicon using Graphene as Buffer Layer / Martin Heilmann ; Gutachter : Gerd Leuchs ». Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1125715472/34.
Texte intégral
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Heilmann, Martin [Verfasser], et Gerd [Gutachter] Leuchs. « Heteroepitaxial Growth of GaN Nanostructures via Metalorganic Vapor Phase Epitaxy on Sapphire and Silicon using Graphene as Buffer Layer / Martin Heilmann ; Gutachter : Gerd Leuchs ». Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1125715472/34.
Texte intégral
26
Fontaine, Chantal. « Heteroepitaxie par jets moeculaires : systeme (ca,sr)f ::(2) - gaas ». Toulouse 3, 1987. http://www.theses.fr/1987TOU30135.
Texte intégralRésumé :
Dans la premiere partie du memoire sont etudies les mecanismes de formation de defauts pendant la croissance cristalline, les contraintes s'exercant sur les couches heteroepitaxiales, la possibilite de relaxation de ces contraintes par creation de defauts ainsi que les solutions pratiques envisagees pour eliminer ces defauts. Dans la seconde partie sont presentes et analyses les resultats experimentaux obtenus sur les structures (ca,sr)f::(2)/gaas et gaas/(ca,sr)f::(2) realisees par epitaxie par jets moleculaires. Sont consideres les proprietes des interfaces, les relations d'epitaxie, les mecanismes de croissance et les contraintes. Finalement, sont discutees les applications potentielles de ce type de structures et leur compatibilite avec les proprietes optiques et electriques des deux materiaux elabores
27
Porte, Agnès. « Determination des parametres qui regissent la cinetique et la composition d'un depot de gainas/inp par la methode aux hydrures ». Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF2D162.
Texte intégralRésumé :
En s'appuyant sur les resultats experimentaux de la croissance de ga::(x)in::(1-x)as/inp en phase vpeur par la methode aux hydrures et sur une theorie cinetique de croisssance qui permet d'exprimer facilement le rapport des pressions partielles de chlorures en fonction de x, detection et analyse de differents phenomenes en jeu dans la croissance. Calcul des parametres necessaires a la prise en compte de ces phenomenes pour la determination des pressions partielles reelles de chacun des constituants de la phase vapeur dans chaque experience realisee. La maitrise de la cinetique du depot et de la composition de la couche de ga::(x)in::(1-x)as est de ce fait rendue possible dans l'epitaxie par la methode aux hydrures
28
Pellissier, Anne. « Etude structurale et microscopique du système Y/Si ». Grenoble INPG, 1989. http://www.theses.fr/1989INPG0031.
Texte intégralRésumé :
Le siliciure ysi 1,7 en phase hexagonale s'epitaxie sur un support si(iii) avec un accord de maille quasi parfait. La couche resultante (100-200 a) contient des grains de 50 a 100 a. Une forte anisotropie de structure de bandes est revelee par photoemission. Les lacunes si s'ordonnent en trois dimensions. Mesures electriques: comportement de type semi-metallique et faible hauteur de barriere de schottky pour le contact ysi 1,7/si dope n. Si peut se reepitaxier sur une couche de siliciure d'y elle-meme epitaxiee sur un support si(iii). Un echantillon est obtenu, avec toutefois des defauts d'empilement dans la couche si. La fabrication de couches multiples de cette nature est envisageable
29
Allain, Laurent. « Etude des effets de la temperature sur la diffraction des rayons x par des composes semiconducteurs iii-v ». Paris 6, 1988. http://www.theses.fr/1988PA066016.
Texte intégralRésumé :
Determination par diffraction rx haute resolution des parametres cristallins de couches epitaxiques de gaalas ou gainas deposees sur les supports si, ge, ga, as, gap, inp et inas, en fonction de la temperature. Les coefficients de dilatation sont determines sur des materiaux relaxes et une extrapolation a d'autres systemes est possible. L'accord parametrique pour gaalas est realise a une temperature superieure a la temperature de depot et pour gainas, cet accord est realise a une temperature de depot dependant du taux de substitution ga/in
30
Fontaine, Christophe. « Hétéroépitaxie par jets moléculaires de semiconducteurs II-VI ». Grenoble 1, 1986. http://www.theses.fr/1986GRE10062.
Texte intégralRésumé :
Etude de l'heteroepitaxie de cdte, cd::(1-x)zn::(x)te et cd::(x)hg::(1-x)te sur cdznte, insb et gaas (001) et (111) et des differents parametres qui gouvernent la qualite cristalline. Il s'avere que la croissance (001) est meilleure que la croissance (111). L'interet d'une interface graduelle est demontre a fort desaccord de maille. A faible desaccord de mailles les contraintes dans les couches epitaxiques ont ete mesurees. Dans ces conditions experimentales, la relaxatioon des couches est gouvernee par un mecanisme de generation de dislocations et non par l'activation thermique des dislocations presentes. Les modeles existants ne permettent pas de decrire la relaxation dans les couches cdte. Presentation d'un modele qui rend compte des observations
31
Robach, Odile. « Étude in situ de la croissance de Ag sur MgO(001) et de Ni/Ag(001), et étude de la nitruration du GaAs par diffusion de rayons X en incidence rasante ». Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10226.
Texte intégralRésumé :
Un nouvel instrument est presente, qui permet l'elaboration d'interfaces dans une chambre ultra-vide et l'etude in situ de leur structure et de leur morphologie par diffusion des rayons x en incidence rasante (dxir). Il est installe sur la ligne de lumiere crg/if d32 de l'esrf. Une nouvelle description du mode de croissance de l'ag sur le mgo est proposee, dans laquelle, des 0. 2 monocouches (mc) d'ag deposees, le depot est sous forme d'ilots et la majorite de l'ag est relaxee. La signification physique de la fraction en site de l'ag est discutee, ainsi que les possibilites de calcul des positions atomiques dans un ilot d'ag deforme par les contraintes d'epitaxie dues au mgo. La preparation de surfaces de mgo bien adaptees aux etudes par dxir est decrite. Les phases presentes dans differents depots de ni sur ag (001) ont ete identifiees et caracterisees. A tous les montants de depots de 1 a 20 mc, trois phases coexistent : du ni en site, du ni (001) relaxe et du ni (011) 4h, qui forment des colonnes s'etendant jusqu'a la surface du depot. Une rugosification de l'ag liee au depot de ni a ete mise en evidence, ainsi que de fortes deformations de l'ag. La nitruration a l'aide d'une source d'azote a resonance cyclotron electronique (ecr) des surfaces (001) et (-1-1-1)b du gaas a ete etudiee. Pour former une couche de gan d'epaisseur bien definie il est preferable de separer la phase d'implantation des atomes d'azote dans le gaas de la phase de recuit declenchant la formation du gan. Des developpements de la technique d'analyse sont presentes, qui concernent en particulier les calculs de resolution instrumentale et l'analyse des donnees de diffusion aux petits angles en incidence rasante.
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Yang, Shang-Shian, et 楊尚賢. « Heteroepitaxial growth on Si：TiN、ZrN、ZnO ». Thesis, 2006. http://ndltd.ncl.edu.tw/handle/15858197115090731845.
Texte intégral
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Hu, Tzu-Chieh, et 胡子杰. « Heteroepitaxial Growth of GaN Using a Ga2O3 Interlayer ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/95851152673068612071.
Texte intégralRésumé :
碩士國立中興大學
精密工程學系所
99
This thesis has presented a new sacrificial material, gallium oxide (Ga2O3) for the chemical lift off (CLO) process of GaN epilayers from sapphire substrates. The atmosphere of metal organic vapor chemical deposition (MOCVD) used for growing crystalline GaN on Ga2O3 sacrificial layer was N2 since a serious degradation of Ga2O3 would take place in a H2 ambient at high temperature. To improve the quality of GaN grown with N2 as carrier gas, the GaN was subsequently regrown in a H2 ambient. In order to increase the lateral etching rate for CLO process conducted with Ga2O3, the SiO2 stripes with a 3-μm-wide, a 400-nm-height, and 3-μm-spacing were deposited on Ga2O3/sapphire in the direction of <11 ¯00>GaN by a combination of plasma enhanced chemical vapor deposition, photolithograph and inductively coupled plasma dry etching processes. The growth of GaN epilayer on the Ga2O3 layer with SiO2 stripes was achieved by the two-step selective MOCVD where the first-step was carried out in a N2 ambient and the second-step was conducted in a H2 ambient. The full width at half maximum of rocking curve at (002) plane for the GaN grown by this 2-step selective MOCVD was 40% lower than that for the GaN grown by a conventional MOCVD in a N2 ambient. Meanwhile, the lateral etching rate of Ga2O3 was dramatically improved since these SiO2 stripes provided hydrofluoric acid pathways for getting into the central part of Ga2O3.
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LIN, JU-SHAN, et 林鉅山. « Heteroepitaxial growth of GaAs on Si(100) substrate ». Thesis, 1992. http://ndltd.ncl.edu.tw/handle/51236705278020045127.
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Chang-Shung, Liang, et 梁家順. « Optimization of heteroepitaxial growth of GaAsP on GaP substrate ». Thesis, 1998. http://ndltd.ncl.edu.tw/handle/34063416972911721965.
Texte intégralRésumé :
碩士中原大學
電子工程研究所
86
III-V ternary and quaternary semiconductor alloy crystals are of vital importance in the fabrication of optoeletronic and high-speed devices since the desired bandgap energy and lattice constant can be achieved by controlling their composition. However, the misfit between the alloy layer and the available binary substrates still remains as the main problem. In the design and fabrication of new alloy devices, the availability of alloy substrates with controlled lattice parameters can remove the limitation of In this study, we will optimize the growth condition of GaAsP epilayer on GaP substrate by using a novel LPE technique, called "composition conversion" for preparing a ternary substrate. This composition converting technique is composed of two steps. First, a GaAs layer is grown on a GaP substrate. Second, the GaAs layer converts its composition to GaAsP alloy when contacts with the saturated Ga-As-P solution. A mechanism of the converting behavior can be understood that P atoms rapid diffuse into the uns Both the growth time of GaAs layer, t1, and the contact time of Ga-As-P solution with the grown GaAs, t2, are varied to achieve the optimum growth conditions of this technique. The variations of both growth times, t1 and t2, for GaAs and GaAsP layers, respectively, are given as follows: 1. growth time of the GaAs layer t1 : 12, 18, 30 (minutes)2. growth time of the GaAsP layer t2 : 12, 30, 60, 78, 90 (minutes) According to the measurement results of x-ray and PL, the optimum conditions for growing GaAs and finally obtaining the GaAsP layers with stable solid composition are determined as:1. The growth time of GaAs, t1≧18 minutes. 2. the conversion time of GaAsP, 60≦t2≦90 minutes.
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CHEN, MIN-YI, et 陳銘逸. « Heteroepitaxial growth of GaInP lattice matched to GaAs by MOCVD ». Thesis, 1993. http://ndltd.ncl.edu.tw/handle/97337731307784286202.
Texte intégral
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Che-YuLin et 林哲聿. « Investigation of GaAs-based material heteroepitaxial growth and device applications ». Thesis, 2012. http://ndltd.ncl.edu.tw/handle/81637226898812179104.
Texte intégralRésumé :
碩士國立成功大學
奈米科技暨微系統工程研究所
100
In this thesis, the main purpose of our research is focused on tuning the epitaxial conditions of nucleation layer to improve the problems of Ge-based solar cells such as APDs and Ge outdiffusion. Therefore, we could tune the epitaxial conditions, and we can apply these parameters to form the high efficiency tandem solar cells in the future. Plenty of material characterization techniques such as atomic force microscopy (AFM), high resolution X-ray diffraction (HR-XRD), and photoluminescence (PL) system have been used to study the quality and characteristics. First, we tried to grow the GaAs nucleation layer on Ge/Si and Ge substrate by MOCVD. Then, we adjusted the V/III ratio, growth temperature, buffer thickness, and misorientation angle to improve the buffer quality. We could observe that when the growth in the low V/III ratio ambience, the lateral growth rate was higher than the vertical growth rate, which would form the flat plane. From the experiments results, if the V/III ratio was too low, it would have the carbon pollution problem and the best V/III ratio was 5. We also observe that when the epitaxial process was in low temperature ambience, the Kinetic energy would be decreased and further cause the atoms diffusion length decreased. But if the growth temperature was too low, the atoms would have not enough energy, so that they could not migrate to find their appropriate sites. And the surface morphology would be worse. We concluded that the appropriate growth temperature was 370℃. From the experiments of varying the buffer thickness, we know the best buffer thickness was 23.5nm through the analysis systems. Finally, we also compared the misorientation angle. From the analysis, we could observe that the 6 degree substrate could let the growth mode become step-flow mode, and the number of APDs would be eliminated. From the results, we could know that the 6 degree substrate was better than the other. We have also studied another nucleation layer material, InGaP. According to the literature, when the layer composition of InGaP got more Ga-rich, the number of arrowhead defects would be increased. So we tuned the layer composition of InGaP to In0.503Ga0.497P. We also have done a series of researches about the InGaP. Through the experiments results, we could observe that when we decreased the growth temperature, the roughness would be increased. It was due to the reduction of PH3 decomposition. Therefore, we adopted the high growth temperature to grow the samples. The material would have the disorder tendency in the high growth temperature ambience. It would also let the solar cell response enhanced by increased minority carrier properties. From the above analysis, we concluded the growth temperature 675℃ was the appropriate growth temperature. Then, we tried to tune the V/III ratio of InGaP material. From the above experiments, we could observe that all the degree of order of InGaP was relatively low. The suitable V/III ratio was 500.4 to achieve the better roughness and crystal quality. In the experiments of varying the buffer thickness, we could observe that the sample with 25 nm buffer layer was the best for both the enhancements of epitaxial and optical characteristics. Finally, because of the phosphorus diffusion length was shorter than arsenic, the InGaP buffer could prevent the Ge diffusion problem. When we used the InGaP buffer, it could eliminate the APDs problem. Therefore, we concluded that the growth of the InGaP nucleation layer on Ge substrate, the optical and crystalline quality were all be enhanced. And we also hope it could enhance the cell performance. In the following, we used the best parameters of GaAs nucleation layer to grow a solar cell, but we could observe that the surface was not mirror-like. The reason of that might be the worse cell performance. Hence, we incorporate 0.5% indium into GaAs base layer and emitter layer to solve the lattice mismatch problem, so that the short circuit current would be increased from 7.19 mA/cm2 to 8.116 mA/cm2, and the efficiency would also be enhanced from 2.02% to 3.02%. We also tried to change the preflow style to improve the diffusion problem, and enhance the cell performance. When we utilized the preflow Ga ML and As ML style, the Ga vacancies of GaAs film would be decreased, and the diffusion length would also be decreased. Because the adoption of this preflow style, the fill-factor would be increased from 53.196% to 68.718%, and the efficiency would also be increased from 3.02% to 3.5%. In the future, we will use the InGaP material instead of GaAs material as the nucleation layer material. Then, the growth of a InGaP buffer solar cell will be continued. And we can further use the 6∘Si substrate to grow a solar cell in order to achieve the purpose of reduce the cost of solar cells. And then we will optimize the InGaP subcell. Finally, we will grow a tandem solar cell.
38
ZHANG, ZHI-HAO, et 張志浩. « Heteroepitaxial growth of ZnSe by low pressure metalorganic chemical vapor deposition ». Thesis, 1988. http://ndltd.ncl.edu.tw/handle/20734399576986599981.
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ZHANG, ZHONG-QING, et 張仲青. « Heteroepitaxial growth of ZnS on Si by metalorganic chemical vapor deposition ». Thesis, 1990. http://ndltd.ncl.edu.tw/handle/96565148404348816092.
Texte intégral
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Chiang, Hsin-Yu, et 江欣諭. « Heteroepitaxial Growth and Annealing of Reactively Sputtered Titanium Nitride on Si (100) ». Thesis, 2019. http://ndltd.ncl.edu.tw/handle/z8fv89.
Texte intégralRésumé :
碩士國立交通大學
工學院半導體材料與製程設備學程
107
This thesis mainly studies the epitaxial TiN growth on Si (100) by reactive DC magnetron sputtering and annealing of grown TiN films by using microwave plasma. The TiN film quality and its stoichiometry were also characterized by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). The first part of the study focuses on the TiN epitaxial film qualities which are varied with the reactive sputtering processing conditions, particularly on the effects of the growth temperature and nitrogen ratio. In the second part, the results of TiN film qualities significantly improved by high temperature annealing using microwave plasma are presented, and a comparison with sputtered films is aslo made. The morphologies, crystallinities, and chemical bonding of the as-sputtered films and annealed films were characterized by atomic force microscopy (AFM), XRD, XPS, and transmission electron microscopy (TEM). The results showed that the TiN film grown Si at substrate temperature of 860°C and with 7% N2 in Ar is of high quality with the lowest full width at half maximum (FWHM) of 0.75° for (002) x-ray rocking cuve (XRC). After annealing , the XRC FWHM decreased further to 0.45°. The X-ray phi-scan results also show that TiN is in epitay with and Si (100) in the epitaxial relationship of TiN (100) // Si (100) and TiN [011] // Si [011]. XPS depth profiles show the stoichiometric ratio of Ti and N is close to 1:1 and the O concnetration is less than 5%. The surface roughness of the TiN film measured by AFM was be 1.9 nm, and the resistivity is 17 μΩ-cm. Cross-setional TEM in atomic resolution shows the TiN is in epitaxy with Si across the interface.
41
Chang, Shou-Zen, et 張守仁. « Heteroepitaxial growth of InGaAs epilayers and its appilication to infrared light-emitting diodes ». Thesis, 1994. http://ndltd.ncl.edu.tw/handle/32397544634151515703.
Texte intégral
42
Liu, Chie-Sheng, et 劉智生. « Heteroepitaxial Growth of SiC and Ge on Si Wafers by Chemical Vapor Deposition ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/93616201296512982889.
Texte intégralRésumé :
博士國立臺灣科技大學
化學工程系
97
The subject of this research is focused on: (1) effect of surface graphitization of the SiC buffer layer on the growth mode and crystallinity 3C-SiC(111) films formed through chemical vapor deposition(CVD); (2) surface carbonization of Si(100) by C2H2 and its effects on the subsequent SiC(100) epitaxial film growth; (3) mechanism of growth of the Ge wetting Layer upon exposure of Si(100)-2 × 1 to GeH4; (4) effect of crystallization of a-Si:H passivation layers on surface recombination velocity for n-type Si solar cells. In the first part, we have grown 3C-SiC(111) films epitaxially on Si(111) through low pressure CVD using SiH4, C2H2, and H2 as reactant gases. We used X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy to investigate the effects of the surface graphitization of the carbonized Si(111) on the mode and crystallinity of the subsequent SiC film growth. A disordered crystalline graphite layer was formed after annealing the as-carbonized Si(111) substrate under a H2 ambient at 1343 K for 5 min. The 3C-SiC(111) film grew on the graphitized buffer layer via a three-dimensional growth; this growth was two-dimensional on the surface that had not been subjected to annealing. This behavior correlated with the different in surface energies of the two types of buffer layer. In the second part, surface carbonization of Si(100) using C2H2 as the carbon source was performed in a cold-wall-type CVD reactor at a low pressure of 5 Torr. The carbonization process as a function of C2H2 partial pressure and treatment time was investigated using XPS. It was found that in comparison with a complete transformation to SiC surface on Si(111) by 8 min treatment of 5×10-2 Torr C2H2 at 1343 K, the carbonization on Si(100) under the same condition forms excessive carbon, plausibly due to the larger C2H2 adsorption heat on Si(100) surface. Reducing C2H2 partial pressure to 1.8×10-3 Torr and treatment time to 2 min was enough for Si(100) to form a saturated carbide layer of about 2.0 nm in thickness. Subsequent 3C–SiC(100) epitaxial film growth was found successful especially on a 10 s carbonization- treated surface that has the least amount of excessive carbon. In the third part, we report the initial reaction kinetics for Ge deposition after exposing a Si(100)-2 × 1 surface to GeH4 in a ultra high vacuum chemical vapor deposition system. The growth rate of Ge, especially at the wetting layer stage, was investigated using in situ XPS to measure the signals for Ge atoms at the onset of deposition. A kinetic study concerning the growth of the wetting layer revealed an activation energy of 30.7 kcal/mol for a ca. 0.2-monolayer Ge coverage. This governing energy barrier correlates well with the results of density functional theory calculations, which suggested that opening of the Si dimer following a H atom migration would be the rate-controlling step for the initial growth of the Ge wetting layer on Si(100)-2 × 1 from GeH4. In addition, two- and three-dimer cluster models provided us with extra dimer units with which to model the H atom migration from GeH3(a) to an open site; this process assists the system to overcome the energy barrier for the opening of the Si dimer bond. The Ge atom then became incorporated into the lattice after ring closure. In the final part, surface passivations for the amorphous/c-Si heterojunction structure of solar cells were performed by plasma enhanced chemical vapor deposition reactor. The correlation of effective carrier lifetime and surface crystallization of the various passivation layers were investigated by microwave photoconductivity decay (µ-PCD) and RHEED. It is found that a-Si:H layer of 5 nm in thickness grown on c-Si showed a crystalline structure even at a low [H2]/[SiH4] dilution ration of 10 and a low substrate temperature of 373 K. Adding oxide of 10 at. % to form a a-SiOx:H was effective in preventing the passivation layer from crystallization. µ-PCD measurements showed that Si wafers with wide bandgap a-SiCxOyNz:H exhibited a high effective carrier lifetime up to 2255 µs. The surface recombination velocity of a-SiCxOyNz:H passivated wafer was calculated as low as 5.5 cm/s, indicating a good surface passivation effect.
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Hu, Tzung-Shin, et 胡宗忻. « A Study on Heteroepitaxial Growth of GaAs Solar Cells on Si Substrates by MOCVD ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/51006951673650842460.
Texte intégralRésumé :
碩士大葉大學
電機工程學系
98
This thesis is mainly present a study on heteroepitaxial growth of GaAs solar cells on Si substrates by MOCVD. Si has attracted attention as an alternative substrate because Si substrate is cheap and light-weight compared with Ge or GaAs substrates. The epitaxial growth of III-V semiconductor multilayer structures on Si is a possibility to reduce the costs for high efficiency III-V solar cell devices. Due to the very large difference in lattice constant (~ 4 %) and thermal expansion (> 100 %) a defect free epitaxy of GaAs on Si is challenging. In order to achieve the same performance for GaAs on Si as for the homoepitaxial growth, two step growth process, thermal cyclic annealing (TCA) and intermediate layer (IL) were investigated to reduce the dislocation density. GaAs solar cells were grown by the optimized conditions and were processed into 5.6 mm × 5.6 mm cells by standard processing techniques and measure under solar simulator. A conversion efficiency of 4.02% was obtained from GaAs solar cells on Si substrate without anti-reflection coating under AM1.5 spectrum. A GaAs solar cell with the same structure was grown on GaAs substrate for comparison and its conversion efficiency was 17.92%. The low efficiency for GaAs cells grown on Si substrates might be attributed to large ohmic contact resistance and high dislocation densities.
44
Piquette, Eric C. « Molecular beam heteroepitaxial growth and characterization of wide band gap semiconductor films and devices ». Thesis, 1999. https://thesis.library.caltech.edu/4687/1/Piquette_ec_1999.pdf.
Texte intégralRésumé :
The thesis consists of two parts. Part I describes work on the molecular beam epitaxial (MBE) growth of GaN, AlN, and Al(x)Ga(1-x)N alloys, as well as efforts in the initial technical development and demonstration of nitride-based high power electronic devices. The major issues pertaining to MBE growth are discussed, including special requirements of the growth system, substrates, film nucleation, n- and p-type doping, and the dependence of film quality on growth parameters. The GaN films were characterized by a variety of methods, including high resolution x-ray diffraction, photoluminescence, and Hall effect measurement. It is found that the film polarity and extended defect density as well as quality of photoluminescence and electrical transport properties depend crucially on how the nitride layer is nucleated on the substrate and how the subsequent film surface morphology evolves, which can be controlled by the growth conditions. A technique is proposed and demonstrated that utilizes the control of morphology evolution to reduce defect density and improve the structural quality of MBE GaN films.
In addition to growth, the design and processing of high voltage GaN Schottky diodes is presented, as well as an experimental study of sputter-deposited ohmic and rectifying metal contacts to GaN. Simple models for high power devices, based on materials properties such as minority carrier diffusion length and critical electric breakdown field, are used to estimate the voltage standoff capability, current carrying capacity, and maximum operating frequency of unipolar and bipolar GaN power devices. The materials and transport properties of GaN pertinent to high power device design were measured experimentally. High voltage Schottky rectifiers were fabricated which verify the impressive electric breakdown field of GaN (2-5 MV/cm). Electron beam induced current (EBIC) experiments were also conducted to measure the minority carrier diffusion length for both electrons and holes in GaN.
Part II of the thesis describes studies of the MBE growth of ZnS and investigations of ZnS/GaN light emitting heterojunctions which show promise for application as blue and green light emitters. Zinc sulfide layers doped with Ag and Al were grown by MBE on sapphire, GaAs, and GaN substrates and characterized by x-ray diffraction and photoluminescence. Preliminary current-voltage and electroluminescence results are presented for a processed ZnS:Al,Ag/GaN:Mg prototype blue light emitting device.
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JIANG, MING-CHIEN, et 江鳴謙. « Heteroepitaxial growth of GaN on (100) and (111)Si substrates by pulsed laser deposition ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/02985481165450241805.
Texte intégralRésumé :
碩士國立中興大學
材料科學與工程學系所
102
In this study, the fabrication of hexagonal GaN on Si(100) and Si(111) templates via pulsed laser deposition (PLD) was employed in the development of GaN-on-Si technology. During the GaN growth process, the deposition conditions were modified to investigate the epilayer characteristics. The optimal GaN quality can be achieved by using the substrate temperature of 1000 ?C, the repetition rate of 5 Hz, and the chamber pressure of 3×10-3 torr. The full-width at half-maximum values for the XRD rocking curves of GaN(002) peak were measured to be 1.07? and 0.79?when the films were grown on Si(100) and Si(111) substrates, respectively. Meanwhile, the surface roughnesses of GaN on these two substrates were 17.7 and 14.3 nm, respectively. Furthermore, the growth mechanism of GaN grown on Si substrate with various growth times was established. With increasing the growth time up to 2 hours, the growth mode of GaN film gradually transformed from island growth to layer growth, resulting from the contributions of PLD growth principle and N2 plasma nitridation. Additionally, the high-temperature (1000?C) PLD process can effectively prevent the melt-back etching between Ga and Si in the GaN growth. Except for the Si(100) and Si(111) substrates, the GaN films were also deposited on the sapphire and GaN template fabricated by metalorganic chemical vapor deposition to compare the qualities of these GaN films. The results indicate that the crystal quality on Si substrate is worse than that on the other two substrates. In the PLD process, the GaN vapor was created as the laser pulse impacted the target, and the formation of GaN grains on substrate was generated via the reaction between the GaN vapor and N2 plasma. Due to the interdiffusion between these GaN grains at a high temperature, the GaN film can be formed. In comparison to the MOCVD technique, the residual stress in the GaN was reduced significantly by using PLD, which can efficiently prevent the crack formation. After the PLD growth for 4 hours, the 4-mm-thick GaN film can be achieved. Furthermore, based on the results, the melt-back etching phenomenon was also avoided via the PLD technique without introducing any interlayer or interruption layer. It reveals that several drawbacks in the GaN-on-Si process can be solved using the PLD technique proposed in this research.
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Fu, Chia-Wei, et 傅家威. « Heteroepitaxial Growth and Annealing of DC Reactive Sputtered Titanium Zirconium Nitride on Si (100) ». Thesis, 2019. http://ndltd.ncl.edu.tw/handle/6ryt84.
Texte intégralRésumé :
碩士國立交通大學
材料科學與工程學系所
108
Titanium Zirconium Nitride (TiZrN) with cubic NaCl structure has been widely applied because it has high melting temperature、high hardness、good biocompatibility and great wear resistance. This thesis studies the epitaxial growth of titanium zirconium nitride (TiZrN) films on Si (100) by DC reactive magnetron sputtering and the effects of microwave plasma on TiZrN. TiZrN films were deposited at near 860C using Ti0.68Zr0.32 alloy target with purity of 99.9 % at various powers, work pressures, film thicknesses and target-substrate distances by DC reactive magnetron sputtering. The first part of this thesis focuses on the influence of different process parameters on the microstate and properties of single-layer TiZrN. In addition, (TiZrN/TiN) multilayer was deposited on Si (100) substrate in order to improve film quality. In the second part, single-layer TiZrN and multilayer were annealed by microwave plasma with gas mixture of N2 and H2 to improve the epitaxial layer quality. The crystallinity, lattice parameter, elemental composition, morphology of both single-layer TiZrN and multilayer (TiZrN/TiN) were characterized by x-ray diffraction (XRD)、scanning electron microscope、atomic force microscope、X-ray photoelectron spectrometry (XPS) and transmission electron microscopy. The electrical resistivitys were measured by four-point probe and Hall effect measurement systems. For single-layer TiZrN, the XRD analysis showed that the lowest full width at half maximum (FWHM) of (200) x-ray rocking cuve (XRC) is 1.18 degree. In addition, (200) XRC FWHM of (TiZrN/TiN) multilayer was 0.99 degree. The epitaxial relationship of TiZrN on the Si (100) substrate is TiN (100) // Si (100) and TiN [011] // Si [011]. XPS analysis showed that the composition ratio of N to (Ti + Zr) was close to 1:1, and composition ratio between Ti and Zr was about 17 : 8. After annealing, the single-layer TiZrN (200) XRC FWHM decreaseed from 1.99 degree to 0.85 degree, with surface roughness (Root Mean Square roughness, rms) about 2.0 nm. For the (TiZrN/TiN) multilayer, microwave plasma annealing can reduce its (200) XRC FWHM from 0.99 degree to 0.79 degree, with the surface roughness about 12.2 nm.
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He, Zun-Wei, et 何尊煒. « Heteroepitaxial growth of β-SiC Films on Si subsrate by SiH4/C2H2 chemical vapor deposition ». Thesis, 1998. http://ndltd.ncl.edu.tw/handle/90273739906809227444.
Texte intégral
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Li, Zhen-Yu, et 李鎮宇. « The study on heteroepitaxial growth of III-V compound semiconductors on Si substrate by AP-MOCVD ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/42217988514913902470.
Texte intégralRésumé :
博士中原大學
電子工程研究所
95
In this thesis, the heteroepitaxial growth of III-V compound semiconductors on Si substrate by atmospheric-pressure metal-organic chemical vapor deposition (AP-MOCVD) is reported. The investigations are focused on the growth of three typical monocrystalline materials including gallium arsenide (GaAs), gallium nitride (GaN) and indium nitride (InN). Besides, the fabrication of two polycrystalline films of GaN and titanium nitride (TiN) will also be described. First for GaAs/Si, high-quality GaAs epilayers with the etch-pit density (EPD) lower than 106 cm-2 have been grown on Si (100) substrate. The Atomic Force Microscopy (AFM) images exhibited that the root-mean-square (RMS) value of the surface morphology was only 1.331 nm. The full width at half maximum (FWHM) of the double crystal X-ray rocking curve in the (400) reflection was about 102 arcsec. A key technology of the use of a-GaAs/a-Si double buffers accompanied by in-situ thermal cyclic annealing treatment was developed to achieve this result. Besides, a well-controlled molten KOH etching technique was established to evaluate the EPD of GaAs epilayer with good reproducibility. Also, the effect of a-GaAs/a-Si double buffers was examined in detail by transmission electron microscopy (TEM). Next, for GaN/Si high quality single crystalline GaN layers were grown on Si (111) substrates by using a silicon nitride (SiNx) buffer achieved through the nitridation of substrate. A strong photoluminescence (PL) emission at 365 nm (3.4 eV) with the FWHM of 61.1 meV was achieved at room temperature when the substrate was nitrided at 950°C for 10 min. Particularly, it was found that a yellow luminescent band disappeared when nitridation was performed at temperatures higher than 950°C. The masking effect of porous SiNx buffer was recognized by TEM observation, which is considered to block the threading dislocations and resulted in goo-quality GaN epilayers. For InN/Si, InN epilayers with the band-gap energy between 0.7 – 0.8 eV have been successfully grown on Si (111) substrates with low-temperature (450�aC) grown InN and high-temperature (1050ºC) grown AlN (InN/AlN) double-buffer layers. X-ray diffraction (XRD) characterizations indicated that highly (0001)-oriented hexagonal InN was grown on Si (111) substrate. Hall measurements showed the mobility and carrier concentration were 87.2 cm2/V-s and (7-8) × 1019 cm-3, respectively. PL analyses performed at room temperature showed a strong emission at 0.72 eV with a full-width at half-maximum of 121 meV. Excitation intensity dependent measurements demonstrated the PL mechanism to be the band-to-band transition. Time-resolved PL could be fitted by a single exponential exhibiting an ordered film and a recombination lifetime of around 0.85 ns. In particular, TEM characterizations indicated that the use of AlN first buffer is effective to obtain an InN epilayer with hexagonal structure. As an option to use GaN, poly-crystalline GaN films were also grown and their optical properties and ohmic contact characteristics were examined. Scanning electron microscopy analyses display that the shape and size of GaN grains are quite dependent on the growth temperature. XRD characterizations show that the polycrystalline GaN exhibits wurtzite structure with a preferential (0001) orientation. PL spectra show a strong yellow luminescence from the poly-GaN films. Furthermore, a low-resistivity ohmic contact to poly-GaN was achieved using the multilayer metal combination of Ti (50Å)/Au (100Å)/Ni (100Å)/Au (3000Å). An improvement in �歊 of over one order of magnitude was achieved over the as-deposited condition with good reproducibility by RTA treatment for a total duration of 120 s. In particular, by optimizing the annealing temperature to 400°C a relatively low �歊 of 1.6×10-5 Ω-cm2 was yielded for the contact of Ti/Au/Ni/Au to poly-GaN with a carrier concentration of (5-6)×1017 cm-3. Finally, for TiN/Si, the TiN films were obtained by exploiting TiCl4+NH3 gas chemistry with flow ratios from [NH3]/[TiCl4]=0.2 to 1.4, and deposition temperatures (Td) from 600 to 900°C. When Td = 800°C gold-colored films with electrical resistivities of under 100 μΩ cm were formed at almost all of the investigated flow ratios. In particular, a lowest resistivity of about 23.7 μΩ cm, which is quite close to that of bulk TiN, was achieved using an flow ratio of 0.3. AFM characterizations indicated that the root mean square surface roughness of that film was only about 5.1 nm. Under the same [NH3]/[TiCl4] flow ratio as above, XRD analyses revealed the presence of a cubic TiN phase with a preferred orientation of (200) for Td < 800°C, while additional (111) and (220) orientations emerged when the film was deposited at 900�aC. In conclusion, a low resistivity (<100 μΩ cm) TiN film can be formed on Si substrate with very low flow ratios [NH3]/[TiCl4]=0.3 – 1.4.
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HSIEH, CHIH-CHIEH, et 謝志傑. « Study of heteroepitaxial growth of In2Se3 on Si substrates by atmospheric-pressure halide chemical vapor deposition ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/33257802894625371301.
Texte intégralRésumé :
碩士中原大學
電子工程研究所
95
Study of heteroepitaxial growth of In2Se3 on Si substrates by atmospheric-pressure halide chemical vapor deposition Abstract Up to now solar cells can be classified into many type according to the materials used, such as silicon, compound semiconductors and organic compounds…etc. (see FigureⅠ). Among these types of solar cells, silicon solar cells can be classed with Crystalline and Amorphous thin film; Crystalline is included single crystalline, poly crystalline and thin film poly. Furthermore, compound also can be classed with single and poly crystalline. Single crystalline compound for example like GaAS, InP…etc. poly crystalline for example like CdS, CIGS (CuInGaSe2) …etc. In the word, there would be developed area whatever any materials of solar cells, and no one could include all. This paper investigated for one of buffer layers In2Se3 which is included of CIGS (CuInGaSe2) thin film Solar cells. All simples were deposited on Si substrates by homemade vertical atmospheric pressure metal-organic Chemical Vapor Deposition (MOCVD) system. The In2Se3 thin films were almost γ-phase. The paper research four parts of experiments: First is In2Se3 films grown with different temperatures. Second is In2Se3 films grown with different Ⅲ-Ⅵ ratio. Third is In2Se3 films grown with different Si substrates. And fourth is In2Se3 films grown with AlN buffer layer. The finally purpose is much understand for In2Se3 to be useful and decreased leakage of electric current of CIGS solar cell.
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LI, NIAN-YI, et 李念宜. « GaSb/GaAs heteroepitaxial growth by metal organic chemical vapor deposition and the study of schottky diodes ». Thesis, 1990. http://ndltd.ncl.edu.tw/handle/47650524725474541941.
Texte intégralRésumé :
碩士國立成功大學
電機工程研究所
78
GaSb-bascd化合物由於具有長波長光響應的特懷, 波長在1.24μm(AtGaSb) 至4.3μm (InCaAsSb)及8 至12μm(InAsSb／InSb量子井應力結構) 範圍內具有極低的傳輸損失 , 其電子與電洞移動率亦高於Inp 系列, 故極適合應用於光電元件的研究。本文係採 用有機金屬汽相沈積法成長銻化鎵(GaSb)同質, 祑質磊晶怪於銻化鎵及砷化鎵基板上 并建立最佳成長條件以做為InAs／GaSb高速元件、InGaSb／GaSb、GaAsSb／GaSb等超 晶格應力結構發展之基礎。 本實驗室自行建立的新MOCVD系統專以研究銻為主的Ⅲ-V 半導體材料, 并對量子井及 超晶格元件之制造上亦有初步的考量與設計, 以期成長高品質, 低背影濃度之磊晶層 。 首先對銻化鎵、砷化鎵基板之清潔步驟及銻化鎵磊晶膜的制程做了詳細的說明, 而后 探討在改變成長參數狀況下, 銻化鎵表面形成及光與電特性之變化。在所有成長條件 下, 銻化鎵晶膜為正型特性, 其在長速率隨〔TEG 〕莫耳分率線性的增加而與〔TMSb 〕菲耳分率無關, 對成長溫度更是密切地相關。〔TMSb〕／〔TEG〕比例在6∼8之間, 可得到鏡似無缺隱的表面, 但過大的莫耳分率將會嚴重地影響到晶膜之品質。 在金屬／銻化鎵蕭基二極體方面, 吾人由不同金屬測量其電流—電壓特性發現不同方 向的銻化鎵基板, 基位障(barrier height)被不同的表面能態(surface states)所箝 住。由於(111)銻化鎵比(100)銻化鎵基板擁有較多的dangling bonds, 而此懸浮的鍵 結容易造成載子的陷阱, 進而箝住金屬與銻化鎵間的能障, 使得吾人難以得到高位障 的蕭基二極體。在熱穩定特性探討中, 吾人發現把／銻化鎵接觸在高溫時(450℃) 易 形成Ga Pd 復合物而將蕭基二極體能障降低形成歐姆接觸, 故利用有限反應(limit r eaction)的觀念研制雙層金／鈀／銻化鎵蕭基二極體, 發現在450 ℃30分鐘退火下, 依然擁有良好的蕭基特性。