Journal articles: 'Heterostructures Heterostructures'

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Maevskaya, Maria V., Aida V. Rudakova, Alexandra V. Koroleva, Aleksandr S. Sakhatskii, Alexei V. Emeline, and Detlef W. Bahnemann. "Effect of the Type of Heterostructures on Photostimulated Alteration of the Surface Hydrophilicity: TiO2/BiVO4 vs. ZnO/BiVO4 Planar Heterostructured Coatings." Catalysts 11, no. 12 (November 23, 2021): 1424. http://dx.doi.org/10.3390/catal11121424.

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Here, we report the results of comparative studies of the photostimulated hydrophilic behavior of heterostructured TiO2/BiVO4 and ZnO/BiVO4, and monocomponent TiO2 and ZnO nanocoating surfaces. The chemical composition and morphology of the synthesized nanocoatings were characterized by XPS, SEM, and AFM methods. The electronic energy structure of the heterostructure components (band gap, top of the valence band, bottom of the conduction band, and Fermi level position) was determined on the basis of experimental results obtained by XPS, UV-V absorption spectroscopy and Kelvin probe methods. According to their electronic energy structure, the ZnO/BiVO4 and TiO2/BiVO4 heterostructures correspond to type I and type II heterostructures, respectively. The difference in the type of heterostructures causes the difference in the charge transfer behavior at heterojunctions: the type II TiO2/BiVO4 heterostructure favors and the type I ZnO/BiVO4 heterostructure prevents the photogenerated hole transfer from BiVO4 to the outer layer of the corresponding metal oxide. The results of the comparative studies show that the interaction of the photogenerated holes with surface hydroxy-hydrated multilayers is responsible for the superhydrophilic surface conversion accompanying the increase of the surface free energy and work function. The formation of the type II heterostructure leads to the spectral sensitization of the photostimulated surface superhydrophilic conversion.

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Huma, Tabasum, Nadimullah Hakimi, Muhammad Younis, Tanzeel Huma, Zhenhua Ge, and Jing Feng. "MgO Heterostructures: From Synthesis to Applications." Nanomaterials 12, no. 15 (August 3, 2022): 2668. http://dx.doi.org/10.3390/nano12152668.

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The energy storage capacity of batteries and supercapacitors has seen rising demand and problems as large-scale energy storage systems and electric gadgets have become more widely adopted. With the development of nano-scale materials, the electrodes of these devices have changed dramatically. Heterostructure materials have gained increased interest as next-generation materials due to their unique interfaces, resilient structures and synergistic effects, providing the capacity to improve energy/power outputs and battery longevity. This review focuses on the role of MgO in heterostructured magnetic and energy storage devices and their applications and synthetic strategies. The role of metal oxides in manufacturing heterostructures has received much attention, especially MgO. Heterostructures have stronger interactions between tightly packed interfaces and perform better than single structures. Due to their typical physical and chemical properties, MgO heterostructures have made a breakthrough in energy storage. In perpendicularly magnetized heterostructures, the MgO’s thickness significantly affects the magnetic properties, which is good news for the next generation of high-speed magnetic storage devices.

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Давыдова, З. "МОДЕЛИРОВАНИЕ И РАСЧЕТ СПЕКТРА ФОТОЛЮМИНЕСЦЕНЦИИ ГЕТЕРОСТРУКТУРЫ С КВАНТОВОЙ ЯМОЙ НА ПРИМЕРЕ ALGaAS/GaAS." EurasianUnionScientists 6, no. 12(81) (January 18, 2021): 30–35. http://dx.doi.org/10.31618/esu.2413-9335.2020.6.81.1163.

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This research aims to improve the available means for characterizing the emission properties of quantum well heterostructures by modeling and calculating the absorption and photoluminescence spectra using the GaAs/AlGaAs heterostructure as an example. Research is conducted based on multilayer heterostructures and heterostructures with quantum wells to develop detectors and emitting elements in the infrared frequency range, pulsed solid-state generators in the millimeter and submillimeter-wave ranges. The study of radiating properties of heterostructures with a quantum well on A3B5 compounds has become widespread [1-3]. It is possible to control the heterostructure's emission frequency by selecting the optimal composition of the wideband semiconductor layer, the level and type of its doping, the doping region, and the quantum well layer width, which is of applied importance for the development of optoelectronic devices. Technologies for manufacturing such heterostructures are labor-intensive, time-consuming, and expensive processes, which contribute to developing methods for modeling and calculating the characteristic frequencies of radiation and absorption of radiation. Based on such calculations, radiating elements of the submicronic wavelength range can be developed based on heterostructures with a quantum well on the A3B5 type compounds. [4]

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Давыдова, З. "MODELING AND CALCULATION OF THE PHOTOLUMINESCENCE SPECTRUM OF A HETEROSTRUCTURE WITH A QUANTUM WELL BY THE EXAMPLE OF ALGaAS / GaAS." EurasianUnionScientists 6, no. 12(81) (January 18, 2021): 30–35. http://dx.doi.org/10.31618/esu.2413-9335.2020.6.81.1172.

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This research aims to improve the available means for characterizing the emission properties of quantum well heterostructures by modeling and calculating the absorption and photoluminescence spectra using the GaAs/AlGaAs heterostructure as an example. Research is conducted based on multilayer heterostructures and heterostructures with quantum wells to develop detectors and emitting elements in the infrared frequency range, pulsed solid-state generators in the millimeter and submillimeter-wave ranges. The study of radiating properties of heterostructures with a quantum well on A3B5 compounds has become widespread [1-3]. It is possible to control the heterostructure's emission frequency by selecting the optimal composition of the wideband semiconductor layer, the level and type of its doping, the doping region, and the quantum well layer width, which is of applied importance for the development of optoelectronic devices. Technologies for manufacturing such heterostructures are labor-intensive, time-consuming, and expensive processes, which contribute to developing methods for modeling and calculating the characteristic frequencies of radiation and absorption of radiation. Based on such calculations, radiating elements of the submicronic wavelength range can be developed based on heterostructures with a quantum well on the A3B5 type compounds. [4]

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Zheng, L., T. T. Li, R. Jin, M. Lei, Y. J. Xu, X. S. Yang, K. Zhao, B. Sun, Y. Zhang, and Y. Zhao. "The interface superconductivity of Bi2Se3/Fe–Se heterostructure." International Journal of Modern Physics B 32, no. 32 (December 30, 2018): 1850355. http://dx.doi.org/10.1142/s0217979218503551.

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Bi2Se3/Fe–Se heterostructures on Si(100) substrates have been prepared by radio frequency magnetron sputtering technique. The thickness of FeSe2 film is an important factor for the properties of Bi2Se3/Fe–Se heterostructures. Our Bi2Se3/Fe–Se heterostructural samples showed ferromagnetism, which increase with increasing thickness of FeSe2 layer. However, when the FeSe2 layer is as thin as 20 nm, superconductivity could be observed through magnetization measurements, due to the existence of superconducting Fe–Se. Thus the Bi2Se3/Fe–Se heterostructure provides an approach to achieve both ferromagnetism and superconductivity simultaneously in interface, as well as to realize the interplay between a superconductor and a topological insulator.

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Smirnov, A. M., A. Yu Ivanov, A. V. Kremleva, Sh Sh Sharofidinov, and A. E. Romanov. "Stress Relaxation Due to Dislocation Formation in Orthorhombic Ga2O3 Films Grown on Al2O3 Substrates." Reviews on Advanced Materials and Technologies 4, no. 3 (2022): 1–6. http://dx.doi.org/10.17586/2687-0568-2022-4-3-1-6.

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We analyze the preference of various types of misfit dislocation (MD) formation in film/substrate κ-Ga2O3/α-Al2O3 and κ (AlxGa1–x)2O3/κ-Al2O3 heterostructures. We consider two possibilities for variation in films growth orientation (defined by inclination angle ϑ) for these heterostructures with inclination axes about either [100] or [010] crystallographic directions. We study dependences of the critical film thickness for MD formation on the inclination angle ϑ for heterostructures under consideration. We find the presence of two special orientations (ϑ ~ 26° for [100] heterostructure, ϑ ~ 28° for [010] heterostructure, and ϑ = 90° for both inclination types) of κ-Ga2O3/α-Al2O3 heterostructures, for which the formation of MDs is energetically unfavorable. We show that formation of pure edge MDs is easier for [010] κ-(AlxGa1–x)2O3/κ-Al2O3 heterostructures than for [100] heterostructures, and it is vice versa for mixed MDs in these heterostructures.

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Chen, Ying Jie, Xue Li, Bao Nan Jia, Chao Dong, Xiao Ning Guan, Xin Zhao, and Li Hong Han. "Optoelectronic properties and interfacial interactions of two-dimensional Cs₂PbX₄–MSe₂ (M = Mo, W) heterostructures." RSC Advances 12, no. 16 (2022): 9883–90. http://dx.doi.org/10.1039/d2ra00595f.

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The PCE of Cs2PbX4–WSe2 heterostructures is larger than the PCE of Cs2PbX4–MoSe2 heterostructures. Cs2PbI4–WSe2 heterostructure has the largest PCE (18%) among Cs2PbX4–MSe2 heterostructures and has great potential application in solar cells.

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Zhang, Jianzhi, Hongfu Huang, Junhao Peng, Chuyu Li, Huafeng Dong, Sifan Kong, Yiyuan Xie, Runqian Wu, Minru Wen, and Fugen Wu. "A Cost-Effective Long-Wave Infrared Detector Material Based on Graphene@PtSe2/HfSe2 Bidirectional Heterostructure: A First-Principles Study." Crystals 12, no. 9 (September 2, 2022): 1244. http://dx.doi.org/10.3390/cryst12091244.

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The Graphene@PtSe2 heterostructure is an excellent long-wave infrared detection material. However, the expensive cost of PtSe2 prevents its widespread use in infrared detection. In this paper, Hf was used to partially replace Pt to form Graphene@(PtSe2)n(HfSe2)4−n (n = 1, 2, and 3) bidirectional heterostructures consisting of graphene and lateral PtSe2/HfSe2 composites based on first-principles calculations. Then, the new bidirectional heterostructures were compared with heterostructures formed by graphene with pure MSe2 (M = Pt, Hf). It was found that the band gaps of the bidirectional heterostructures were between those of Graphene@PtSe2 and Graphene@HfSe2. Among these heterostructures, the Graphene@(PtSe2)3(HfSe2)1 bidirectional heterostructure has almost the same optical absorption properties in the infrared wavelength region of 1.33~40 µm as the Graphene@PtSe2 heterostructure, and it improves the absorption in the near-infrared wavelength region of 0.75~1.33 µm. Such a designment may bring the material costs down (since PtSe2 costs approximately five times more than HfSe2). This study on the designment of the bidirectional Graphene@(PtSe2)3(HfSe2)1 heterostructure also illustrates a cost-effective design method for Pt-based IR detectors.

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Dadsetani, M., and A. R. Omidi. "Optical filtering properties of TiO2/Al2O3 heterostructures from first principles." International Journal of Modern Physics B 29, no. 06 (March 2, 2015): 1550047. http://dx.doi.org/10.1142/s0217979215500472.

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This study combines the use of the full potential linear-augmented plane wave method (FP-LAPW) within the framework of the density functional theory (DFT) and the optical matrix approach for modeling the multilayer assembly. A new class of heterostructures with sufficient number of alternating layers of rutile- TiO 2 (as a high index material) and α- Al 2 O 3 (as a low index material) are proposed and their transmittance spectra are investigated. This study shows that the number of alternating layers, and the thickness and arrangement of them should be considered in making a heterostructured filter. The relation between heterostructure parameters and narrow-band-pass peaks of transmittance spectra is investigated. The proposed model seems to be successful in predicting the optical behavior of heterostructures and simulations agree well with the experimental observations. In addition, our model is very flexible and the effect of other parameters such as incident angle and light polarization can be easily investigated.

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Murashkina, Anna A., Tair V. Bakiev, Yurii M. Artemev, Aida V. Rudakova, Alexei V. Emeline, and Detlef W. Bahnemann. "Photoelectrochemical Behavior of the Ternary Heterostructured Systems CdS/WO3/TiO2." Catalysts 9, no. 12 (November 27, 2019): 999. http://dx.doi.org/10.3390/catal9120999.

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In this article, we report the results of comparative studies of photoelectrochemical behavior of the binary CdS/TiO2 and WO3/TiO2 and ternary CdS/WO3/TiO2 heterostructures based on titania nanotube and planar structures. Physical–chemical characterization by XRD, XPS, and electron microscopy methods together with electrochemical impedance spectroscopy measurements confirm a successful formation of heterostructured electrodes, both nanotube-based and planar. The results of photoelectrochemical studies of the heterostructures demonstrate a significant difference in their behavior depending on the structure geometry and the character of the formed heterojunctions. It is concluded that nanotube-based heterostructure electrodes can be characterized by a stochastic set of different heterojunctions while planar systems demonstrate well-ordered heterojunctions with a strictly defined electron transfer direction. Particularly, we demonstrate the possibility of the realization of Z-scheme of photoexcitation and charge separation in ternary planar systems under visible light irradiation.

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Li, Jialin, Lizhen Wang, Yuzhong Chen, Yujie Li, Haiming Zhu, Linjun Li, and Limin Tong. "Interfacial Charge Transfer and Ultrafast Photonics Application of 2D Graphene/InSe Heterostructure." Nanomaterials 13, no. 1 (December 28, 2022): 147. http://dx.doi.org/10.3390/nano13010147.

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Interface interactions in 2D vertically stacked heterostructures play an important role in optoelectronic applications, and photodetectors based on graphene/InSe heterostructures show promising performance nowadays. However, nonlinear optical property studies based on the graphene/InSe heterostructure are insufficient. Here, we fabricated a graphene/InSe heterostructure by mechanical exfoliation and investigated the optically induced charge transfer between graphene/InSe heterostructures by taking photoluminescence and pump–probe measurements. The large built-in electric field at the interface was confirmed by Kelvin probe force microscopy. Furthermore, due to the efficient interfacial carrier transfer driven by the built-in electric potential (~286 meV) and broadband nonlinear absorption, the application of the graphene/InSe heterostructure in a mode-locked laser was realized. Our work not only provides a deeper understanding of the dipole orientation-related interface interactions on the photoexcited charge transfer of graphene/InSe heterostructures, but also enriches the saturable absorber family for ultrafast photonics application.

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Degaga, Gemechis D., Sumandeep Kaur, Ravindra Pandey, and John A. Jaszczak. "First-Principles Study of a MoS2-PbS van der Waals Heterostructure Inspired by Naturally Occurring Merelaniite." Materials 14, no. 7 (March 27, 2021): 1649. http://dx.doi.org/10.3390/ma14071649.

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Vertically stacked, layered van der Waals (vdW) heterostructures offer the possibility to design materials, within a range of chemistries and structures, to possess tailored properties. Inspired by the naturally occurring mineral merelaniite, this paper studies a vdW heterostructure composed of a MoS2 monolayer and a PbS bilayer, using density functional theory. A commensurate 2D heterostructure film and the corresponding 3D periodic bulk structure are compared. The results find such a heterostructure to be stable and possess p-type semiconducting characteristics. Due to the heterostructure’s weak interlayer bonding, its carrier mobility is essentially governed by the constituent layers; the hole mobility is governed by the PbS bilayer, whereas the electron mobility is governed by the MoS2 monolayer. Furthermore, we estimate the hole mobility to be relatively high (~106 cm2V−1s−1), which can be useful for ultra-fast devices at the nanoscale.

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Ren, Kai, Ruxin Zheng, Peng Xu, Dong Cheng, Wenyi Huo, Jin Yu, Zhuoran Zhang, and Qingyun Sun. "Electronic and Optical Properties of Atomic-Scale Heterostructure Based on MXene and MN (M = Al, Ga): A DFT Investigation." Nanomaterials 11, no. 9 (August 30, 2021): 2236. http://dx.doi.org/10.3390/nano11092236.

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After the discovery of graphene, a lot of research has been conducted on two-dimensional (2D) materials. In order to increase the performance of 2D materials and expand their applications, two different layered materials are usually combined by van der Waals (vdW) interactions to form a heterostructure. In this work, based on first-principles calculation, some charming properties of the heterostructure constructed by Hf2CO2, AlN and GaN are addressed. The results show that Hf2CO2/AlN and Hf2CO2/GaN vdW heterostructures can keep their original band structure shape and have strong thermal stability at 300 K. In addition, the Hf2CO2/MN heterostructure has I-type band alignment structure, which can be used as a promising light-emitting device material. The charge transfer between the Hf2CO2 and AlN (or GaN) monolayers is 0.1513 (or 0.0414) |e|. The potential of Hf2CO2/AlN and Hf2CO2/GaN vdW heterostructures decreases by 6.445 eV and 3.752 eV, respectively, across the interface. Furthermore, both Hf2CO2/AlN and Hf2CO2/GaN heterostructures have remarkable optical absorption capacity, which further shows the application prospect of the Hf2CO2/MN heterostructure. The study of this work provides theoretical guidance for the design of heterostructures for use as photocatalytic and photovoltaic devices.

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Chopra, Nitin, Yuan Li, and Kuldeep Kumar. "Cobalt oxide-tungsten oxide nanowire heterostructures: Fabrication and characterization." MRS Proceedings 1675 (2014): 191–96. http://dx.doi.org/10.1557/opl.2014.863.

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ABSTRACTNanowire heterostructures comprised of cobalt oxide and tungsten oxide were fabricated in a core/shell configuration. This was achieved by sputter coating tungsten oxide shells on standing cobalt oxide nanowires on a substrate. To ensure the polycrystallinity of tungsten oxide shell, the nanowire heterostructures were subjected to post-sputtering annealing process. The cobalt oxide nanowires for this study were grown employing a thermal method via vapor-solid growth mechanism. The crystal structures, morphologies, dimensions, and phases at various growth stages of nanowire heterostructures were studied using high resolution electron microscopy, energy dispersive spectroscopy, and X-ray diffraction methods. The interfaces of these nanowire heterostructures were also studied and showed variation in the lattice spacing across the heterostructure diameter. Results indicated that the cobalt oxide nanowires survived multiple processing steps and resulted in stable heterostructure configurations. The investigation shows, for the first time, a dry processing route for the formation of such novel nanowire heterostructures.

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El-Sayed, Marwa A., Andrey P. Tselin, Georgy A. Ermolaev, Mikhail K. Tatmyshevskiy, Aleksandr S. Slavich, Dmitry I. Yakubovsky, Sergey M. Novikov, Andrey A. Vyshnevyy, Aleksey V. Arsenin, and Valentyn S. Volkov. "Non-Additive Optical Response in Transition Metal Dichalcogenides Heterostructures." Nanomaterials 12, no. 24 (December 13, 2022): 4436. http://dx.doi.org/10.3390/nano12244436.

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Van der Waals (vdW) heterostructures pave the way to achieve the desired material properties for a variety of applications. In this way, new scientific and industrial challenges and fundamental questions arise. One of them is whether vdW materials preserve their original optical response when assembled in a heterostructure. Here, we resolve this issue for four exemplary monolayer heterostructures: MoS2/Gr, MoS2/hBN, WS2/Gr, and WS2/hBN. Through joint Raman, ellipsometry, and reflectance spectroscopies, we discovered that heterostructures alter MoS2 and WS2 optical constants. Furthermore, despite the similarity of MoS2 and WS2 monolayers, their behavior in heterostructures is markedly different. While MoS2 has large changes, particularly above 3 eV, WS2 experiences modest changes in optical constants. We also detected a transformation from dark into bright exciton for MoS2/Gr heterostructure. In summary, our findings provide clear evidence that the optical response of heterostructures is not the sum of optical properties of its constituents.

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You, Siwen, Xiao Guo, Junjie Jiang, Dingbang Yang, Mingjun Li, Fangping Ouyang, Haipeng Xie, Han Huang, and Yongli Gao. "Temperature−Dependent Raman Scattering Investigation on vdW Epitaxial PbI2/CrOCl Heterostructure." Crystals 13, no. 1 (January 6, 2023): 104. http://dx.doi.org/10.3390/cryst13010104.

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Van der Waals (vdW) epitaxial growth provides an efficient strategy to prepare heterostructures with atomically and electronically sharp interfaces. Herein, PbI2 was in situ thermally deposited onto exfoliated thin−layered CrOCl nanoflakes in high vacuum to fabricate vdW PbI2/CrOCl heterostructures. Optical microscopy, atomic force microscopy, X−ray diffraction, and temperature−dependent Raman spectroscopy were used to investigate the structural properties and phonon behaviors of the heterostructures. The morphology of PbI2 films on the CrOCl substrate obviously depended on the substrate temperature, changing from hemispherical granules to 2D nanoflakes with flat top surfaces. In addition, anomalous blueshift of the Ag1 and Au2 modes as the temperature increased in PbI2/CrOCl heterostructure was observed for the first time. Our results provide a novel material platform for the vdW heterostructure and a possible method for optimizing heterostructure growth behaviors.

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Wang, Xuewen, Gang Liu, Zhi-Gang Chen, Feng Li, Gao Qing Lu, and Hui-Ming Cheng. "Highly efficient H2 evolution over ZnO-ZnS-CdS heterostructures from an aqueous solution containing SO32- and S2- ions." Journal of Materials Research 25, no. 1 (January 2010): 39–44. http://dx.doi.org/10.1557/jmr.2010.0018.

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ZnO-ZnS-CdS heterostructure photocatalysts for water splitting were designed and prepared by a wet chemistry method. It was found that ZnO-ZnS-CdS heterostructures are highly active photocatalysts for H2 evolution under simulated solar light irradiation in an aqueous solution containing SO32- and S2- ions as sacrificial reagents. H2 evolution with (ZnO)2-(ZnS)1-(CdS)1 heterostructure reaches up to 2790 μmol h−1 g−1. The photoexcited electrons in the ZnO-ZnS-CdS heterostructures have a much longer lifetime (>225 ns) than that of the sole ZnO, ZnS, and CdS (<65 ns). The favorable interface processes of the heterostructures make a significant contribution to high photocatalytic H2 evolution rate.

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Pankratov, Evgeny L. "On the influence of mismatch-induced stresses on the I–V characteristics of p–n junctions manufactured in a heterostructure." Multidiscipline Modeling in Materials and Structures 18, no. 2 (March 21, 2022): 262–76. http://dx.doi.org/10.1108/mmms-12-2021-0207.

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PurposeIn this paper, we consider p–n-junctions, manufactured by diffusion or ion implantation in a heterostructures. We analyzed influence of existing in heterostructure mismatch induced stresses on the current-voltage characteristics of the p–n-junctions. We also introduce an analytical approach for analysis of mass and heat transfer in heterostructures with account changes of their parameters on time, as well as their nonlinearity and mismatch induced stresses. In this paper we introduce an analytical approach for prognosis of the considered processes.Design/methodology/approachIn this paper, we consider p–n-junctions, manufactured by diffusion or ion implantation in a heterostructures. We analyzed influence of existing in heterostructure missmatch induced stresses on the current-voltage characteristics of the p–n-junctions. We also introduce an analytical approach for analysis of mass and heat transfer in heterostructures with account changes of their parameters on time, as well as their nonlinearity and missmatch induced stresses. In this paper we introduce an analytical approach for prognosis of the considered processes.FindingsIn this paper, we consider p–n-junctions, manufactured by diffusion or ion implantation in a heterostructures. We analyzed influence of existing in heterostructure missmatch induced stresses on the current-voltage characteristics of the p–n-junctions. We also introduce an analytical approach for analysis of mass and heat transfer in heterostructures with account changes of their parameters on time, as well as their nonlinearity and missmatch induced stresses. In this paper we introduce an analytical approach for prognosis of the considered processes.Originality/valueThis paper is original.

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Xiao, Haodong, Lin Lin, Jia Zhu, Junxiong Guo, Yizhen Ke, Linna Mao, Tianxun Gong, Huanyu Cheng, Wen Huang, and Xiaosheng Zhang. "Highly sensitive and broadband photodetectors based on WSe₂/MoS₂ heterostructures with van der Waals contact electrodes." Applied Physics Letters 121, no. 2 (July 11, 2022): 023504. http://dx.doi.org/10.1063/5.0100191.

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A nanoscale photodetector is a crucial part of intelligent imaging and wireless communication devices. Building van der Waals (vdWs) heterostructures based on two-dimensional transition metal dichalcogenides is thought to be a smart approach for achieving nanoscale photodetectors. However, the pinning effect induced by surface states, defects, and metal-induced gap states during the fabrication process of vdWs heterostructures and contacting electrodes leads to a large Schottky barrier and consequently limits the photoresponse of vdWs heterostructures. In this study, a photodetector based on the WSe2/MoS2 heterostructure with graphene (Gr)/indium tin oxide (ITO) hybrid electrodes has been fabricated. The vdWs contacts established between the exfoliated graphene layers and WSe2/MoS2 heterostructure are able to get rid of lattice damages caused by atom bombardment during the deposition of metal electrodes. In addition, the reduced Schottky barrier at graphene/heterostructure interfaces facilitates the transport of carriers. Experimental results show that the photodetector based on WSe2/MoS2 heterostructures with Gr/ITO hybrid electrodes exhibits a high responsivity of up to 1236.5 A W−1, a detectivity of up to 1.23 × 1013 Jones, and a fast response of 270/130 μs to light from the ultraviolet to near-infrared range.

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Tang, Hongyu, and Giulia Tagliabue. "Tunable photoconductive devices based on graphene/WSe₂ heterostructures." EPJ Web of Conferences 266 (2022): 09010. http://dx.doi.org/10.1051/epjconf/202226609010.

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Optoelectronic tunability in van der Waals heterostructures is essential for their optoelectronic applications. In this work, tunable photoconductive properties were investigated in the heterostructures of WSe2 and monolayer graphene with different stacking orders on SiO2/Si substrates. Here, we demonstrated the effect of the material thickness of WSe2 and graphene on the interfacial charge transport, light absorption, and photoresponses. The results showed that the WSe2/graphene heterostructure exhibited positive photoconductivity after photoexcitation, while negative photoconductivity was observed in the graphene/WSe2 heterostructures. The tunable photoconductive behaviors provide promising potential applications of van der Waals heterostructures in optoelectronics. This work has guiding significance for the realization of stacking engineering in van der Waals heterostructures.

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van Deurzen, Len, Ryan Page, Vladimir Protasenko, Kazuki Nomoto, Huili (Grace) Xing, and Debdeep Jena. "Optically pumped deep-UV multimode lasing in AlGaN double heterostructure grown by molecular beam homoepitaxy." AIP Advances 12, no. 3 (March 1, 2022): 035023. http://dx.doi.org/10.1063/5.0085365.

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Multimode lasing at sub-300 nm wavelengths is demonstrated by optical pumping in AlGaN heterostructures grown on single-crystal AlN substrates by plasma-assisted molecular beam epitaxy. Edge-emitting ridge-based Fabry–Pérot cavities are fabricated with the epitaxial AlN/AlGaN double heterostructure by a combined inductively coupled plasma reactive ion etch and tetramethylammonium hydroxide etch. The emitters exhibit peak gain at 284 nm and modal linewidths on the order of 0.1 nm at room temperature. The applied growth technique and its chemical and heterostructural design characteristics offer certain unique capabilities toward further development of electrically injected AlGaN laser diodes.

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Liu, Xiaoyan, Siyi Lv, Baoyan Fan, An Xing, and Bi Jia. "Ferroelectric Polarization-Enhanced Photocatalysis in BaTiO3-TiO2 Core-Shell Heterostructures." Nanomaterials 9, no. 8 (August 3, 2019): 1116. http://dx.doi.org/10.3390/nano9081116.

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Suppressing charge recombination and improving carrier transport are key challenges for the enhancement of photocatalytic activity of heterostructured photocatalysts. Here, we report a ferroelectric polarization-enhanced photocatalysis on the basis of BaTiO3-TiO2 core-shell heterostructures synthesized via a hydrothermal process. With an optimal weight ratio of BaTiO3 to TiO2, the heterostructures exhibited the maximum photocatalytic performance of 1.8 times higher than pure TiO2 nanoparticles. The enhanced photocatalytic activity is attributed to the promotion of charge separation and transport based on the internal electric field originating from the spontaneous polarization of ferroelectric BaTiO3. High stability of polarization-enhanced photocatalysis is also confirmed from the BaTiO3-TiO2 core-shell heterostructures. This study provides evidence that ferroelectric polarization holds great promise for improving the performance of heterostructured photocatalysts.

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Бабичев, А. В., А. С. Курочкин, Е. С. Колодезный, А. В. Филимонов, А. А. Усикова, В. Н. Неведомский, А. Г. Гладышев, et al. "Гетероструктуры одночастотных и двухчастотных квантово-каскадных лазеров." Физика и техника полупроводников 52, no. 6 (2018): 597. http://dx.doi.org/10.21883/ftp.2018.06.45922.8751.

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AbstractThe results of development of the basic structure and technological conditions of growing heterostructures for single- and dual-frequency quantum-cascade lasers are reported. The heterostructure for a dual-frequency quantum-cascade laser includes cascades emitting at wavelengths of 9.6 and 7.6 μm. On the basis of the suggested heterostructure, it is possible to develop a quantum-cascade laser operating at a difference frequency of 8 THz. The heterostructures for the quantum-cascade laser are grown using molecularbeam epitaxy. The methods of X-ray diffraction and emission electron microscopy are used to study the structural properties of the fabricated heterostructures. Good agreement between the specified and realized thicknesses of the epitaxial layers and a high uniformity of the chemical composition and thicknesses of the epitaxial layers over the area of the heterostructure is demonstrated. A stripe-structured quantum-cascade laser is fabricated; its generation at a wavelength of 9.6 μm is demonstrated.

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24

Блохин, С. А., В. Н. Неведомский, М. А. Бобров, Н. А. Малеев, А. А. Блохин, А. Г. Кузьменков, А. П. Васильев, et al. "Вертикально-излучающие лазеры спектрального диапазона 1.55 мкм, изготовленные по технологии спекания гетероструктур, выращенных методом молекулярно-пучковой эпитаксии из твердотельных источников." Физика и техника полупроводников 54, no. 10 (2020): 1088. http://dx.doi.org/10.21883/ftp.2020.10.49947.9463.

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The GaAs-InGaAsP heterointerfaces formation have been studied and optimized using a direct intermolecular wafer bonding (fusion)of an active region heterostructure on an InP substrate and distributed Bragg reflector heterostructures on GaAs substrates for the fabrication of hybrid heterostructures of long-wave vertical-cavity surface-emitting lasers (VCSEL). The heterostructures were grown by solid-source molecular beam epitaxy. It was shown that in the case of incomplete removal of oxide films during the preparation of the wafers before fusion and/or the presence of adsorbed water on the wafer surfaces, the fused interface contains a large number of amorphous inclusions, most likely related to the III-group oxides. Optimization of the formation regimes of a buried tunnel junction on the surface of the InP-based heterostructure made it possible to reduce the surface roughness down to 1 nm and to ensure the thickness of the GaAs-InGaAsP fused interface < 5 nm, with no dislocations or other extended defects in the region of the fused heterointerfaces. The 1.55 μm-range VCSELs fabricated from the hybrid heterostructures created by using the developed technology demonstrate efficient lasing under continuous wave pumping over a wide temperature range, which indicates the high optical quality of the fused heterointerfaces in the VCSEL heterostructure.

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Gladysheva, Nadezhda B., Vadim V. Gruzdov, Yurii V. Kolkovskii, Yulii A. Kontsevoy, and Evgenii F. Pevtsov. "Control of yellow photoluminescence in AlGaN/GaN heterostructures." Modern Electronic Materials 5, no. 2 (June 1, 2019): 87–89. http://dx.doi.org/10.3897/j.moem.5.2.51391.

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Photoluminescence with the peak corresponding to yellow color of the visible spectrum (so-called yellow luminescence) originates from deep levels in the GaN buffer layers of heterostructures and depends on heterostructure growth conditions. In turn deep levels affect the resistance of Ohmic contacts of microwave transistors fabricated from these heterostructures. This determines the reliability of GaN microwave transistor operation. Two types of units for control of photoluminescence with the peak in the yellow visible spectral region have been designed with the aim to control the quality of AlGaN/GaN/SiC and AlGaN/GaN/Al2O3 heterostructures. One of the units is used for fast control of yellow photoluminescence and the other for photoluminescence mapping on heterostructure wafer surfaces. Examples of photoluminescence maps for structures grown on different substrates have been given.

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26

Sharma, Bharat, Ashutosh Sharma, Monika Joshi, and Jae-ha Myung. "Sputtered SnO2/ZnO Heterostructures for Improved NO2 Gas Sensing Properties." Chemosensors 8, no. 3 (August 7, 2020): 67. http://dx.doi.org/10.3390/chemosensors8030067.

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A highly sensitive and selective NO2 gas sensor dependent on SnO2/ZnO heterostructures was fabricated using a sputtering process. The SnO2/ZnO heterostructure thin film samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Sensors fabricated with heterostructures attained higher gas response (S = 66.9) and quicker response-recovery (20 s, 45 s) characteristics at 100 °C operating temperature towards 100 ppm NO2 gas efficiently in comparison to sensors based on their mono-counterparts. The selectivity and stability of SnO2/ZnO heterostructures were studied. The more desirable sensing mechanism of SnO2/ZnO heterostructures towards NO2 was described in detail.

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Trenczek-Zajac, Anita, Joanna Banas-Gac, and Marta Radecka. "TiO2@Cu2O n-n Type Heterostructures for Photochemistry." Materials 14, no. 13 (July 2, 2021): 3725. http://dx.doi.org/10.3390/ma14133725.

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A TiO2@Cu2O semiconductor heterostructure with better photochemical response compared to TiO2 was obtained using an electrochemical deposition method of Cu2O on the surface of TiO2 nanotubes. The choice of 1D nanotubes was motivated by the possibility of achieving fast charge transfer, which is considered best suited for photochemical applications. The morphology and structural properties of the obtained heterojunction were determined using standard methods —SEM and Raman spectroscopy. Analysis of photoelectrochemical properties showed that TiO2@Cu2O heterostructures exhibit better properties resulting from an interaction with sunlight than TiO2. A close relationship between the morphology of the heterostructures and their photoproperties was also demonstrated. Investigations representing a combination of photoelectrochemical cells for hydrogen production and photocatalysis—photoelectrocatalysis—were also carried out and confirmed the observations on the photoproperties of heterostructures. Analysis of the Mott–Schottky plots as well as photoelectrochemical measurements (Iph-V, Iph-t) showed that TiO2 as well as, unusually, Cu2O exhibit n-type conductivity. On this basis, a new energy diagram of the TiO2@Cu2O system was proposed. It was found that TiO2@Cu2O n-n type heterostructure prevents the processes of photocorrosion of copper(I) oxide contained in a TiO2-based heterostructure.

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Maeda, Narihiko, Tadashi Saitoh, Kotaro Tsubaki, Toshio Nishida, and Naoki Kobayashi. "Two-Dimensional Electron Gas Transport Properties in AlGaN/(In)GaN/AlGaN Double-Heterostructure Field Effect Transistors." MRS Internet Journal of Nitride Semiconductor Research 5, S1 (2000): 362–68. http://dx.doi.org/10.1557/s1092578300004518.

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Two-dimensional electron gas transport properties have been investigated in nitride double-heterostructures. A striking effect has been observed that the two-dimensional electron gas mobility has been drastically enhanced in the AlGaN/GaN/AlGaN double-heterostructure, compared with that in the conventional AlGaN/GaN single-heterostructure. The observed mobility enhancement has been shown to be mainly due to the enhanced polarization-induced electron confinement in the double-heterostructure, and additionally due to the improvement of the interface roughness in the structure. Device operation of an AlGaN/GaN/AlGaN double-heterostructure field effect transistor has been demonstrated: a maximum transconductance of 180 mS/mm has been obtained for a 0.4 μm-gate-length device. In the double-heterostructure using InGaN channel, the increased capacity for the two-dimensional electron gas has been observed. The AlGaN/(In)GaN/AlGaN double-heterostructures are effective for improving the electron transport properties.

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29

Zhang, Yong-Qiang, Xiao-Hui Li, Fen-Fen Li, Jie Lv, Guang-Jun Liu, and Hong-Tao Gao. "The study on the geometry and electronic properties of (WO3)x/(TiO2)y heterostructure by using the layered structural model." Journal of Theoretical and Computational Chemistry 13, no. 05 (August 2014): 1450034. http://dx.doi.org/10.1142/s0219633614500345.

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The layered structural model was proposed to study the geometry and electronic properties of the ( WO 3)x/( TiO 2)y heterostructures in this paper. The geometry and electronic properties were affected greatly by the relative proportion of TiO 2 and WO 3 in the nanocomposites. The minimum band gap of ( WO 3)x/( TiO 2)y heterostructures decreased with the proportion of WO 3 increasing but increased with the proportion of TiO 2 increasing. Interestingly, electrons at the upper valence band (VB) can be directly excited from 2p and 3d orbitals of titania to the conduction band (CB), which was mainly consisted of 5d orbitals of tungsten trioxide. The effective electron mass of ( WO 3)x/( TiO 2)y heterostructures was higher than that of pure TiO 2. It indicated that the electron–hole recombination rate of hybrid ( WO 3)x/( TiO 2)y heterostructure was lower than that of pure TiO 2, which might imply that photocatalytic activities of the hybrid ( WO 3)x/( TiO 2)y heterostructures were enhanced under visible light irradiation. The theoretical results might offer a new useful guide for designing semiconductors photocatalyst, such as heterostructure nanocomposites.

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Смирнов, А. М., А. В. Кремлева, Ш. Ш. Шарофидинов, В. Е. Бугров, and А. Е. Романов. "Релаксация напряжений несоответствия в гетероструктурах alpha-Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-/alpha-Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- при образовании дислокаций несоответствия." Физика твердого тела 63, no. 6 (2021): 788. http://dx.doi.org/10.21883/ftt.2021.06.50941.029.

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We propose the analytical models describing misfit stress relaxation in α-Ga2O3/α-Al2O3 film/substrate heterostructures taking into account the crystal lattices anisotropy of the heterostructure materials. We consider the nucleation of misfit dislocations as a result of basal or prismatic slip in α-Ga2O3/α-Al2O3 heterostructures with various film orientations. We calculate and analyze the dependences of the critical thickness hc (film thickness above which the nucleation of misfit dislocations is favorable) on the angle ϑ between the polar c-axis and the normal to the film growth plane for α-Ga2O3/α-Al2O3 heterostructures. We demonstrate that accounting for elastic constant C14 is not critical in the considered relaxation models for the α Ga2O3/α Al2O3 heterostructures.

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Turfanda, Aykut, and Hilmi Ünlü. "Single atom precise, ultrafast, and universal emulation of biological synapses using atomically thin vertical heterostructures." Journal of Applied Physics 132, no. 12 (September 28, 2022): 124306. http://dx.doi.org/10.1063/5.0112920.

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We propose three vertical heterostructures of two-dimensional materials composed of MoS[Formula: see text] and AlN single layers to emulate biological synaptic behaviors. We aim to show a so-called healthy synaptic behavior with an N vacancy-defected heterostructure, dysfunctional synaptic behavior with a pristine heterostructure, and repaired synaptic behaviors using an N intercalated heterostructure. We compare the abilities of those proposed artificial synapses using density functional theory, Boltzmann transport methods, and real-time time dependent density functional theory. We find that the vacancy-defected heterostructure can mimic the biological synaptic behaviors better than the others. We conclude a relation between learning abilities and synaptic abilities. A combination of logic and memory abilities is positively correlated with synaptic abilities. These results are significant to emulate the brain on a large scale, with ultrathin and low power consumption heterostructures.

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Slepchenkov, Michael M., Dmitry A. Kolosov, Igor S. Nefedov, and Olga E. Glukhova. "Band Gap Opening in Borophene/GaN and Borophene/ZnO Van der Waals Heterostructures Using Axial Deformation: First-Principles Study." Materials 15, no. 24 (December 13, 2022): 8921. http://dx.doi.org/10.3390/ma15248921.

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One of the topical problems of materials science is the production of van der Waals heterostructures with the desired properties. Borophene is considered to be among the promising 2D materials for the design of van der Waals heterostructures and their application in electronic nanodevices. In this paper, we considered new atomic configurations of van der Waals heterostructures for a potential application in nano- and optoelectronics: (1) a configuration based on buckled triangular borophene and gallium nitride (GaN) 2D monolayers; and (2) a configuration based on buckled triangular borophene and zinc oxide (ZnO) 2D monolayers. The influence of mechanical deformations on the electronic structure of borophene/GaN and borophene/ZnO van der Waals heterostructures are studied using the first-principles calculations based on density functional theory (DFT) within a double zeta plus polarization (DZP) basis set. Four types of deformation are considered: uniaxial (along the Y axis)/biaxial (along the X and Y axes) stretching and uniaxial (along the Y axis)/biaxial (along the X and Y axes) compression. The main objective of this study is to identify the most effective types of deformation from the standpoint of tuning the electronic properties of the material, namely the possibility of opening the energy gap in the band structure. For each case of deformation, the band structure and density of the electronic states (DOS) are calculated. It is found that the borophene/GaN heterostructure is more sensitive to axial compression while the borophene/ZnO heterostructure is more sensitive to axial stretching. The energy gap appears in the band structure of borophene/GaN heterostructure at uniaxial compression by 14% (gap size of 0.028 eV) and at biaxial compression by 4% (gap size of 0.018 eV). The energy gap appears in the band structure of a borophene/ZnO heterostructure at uniaxial stretching by 10% (gap size 0.063 eV) and at biaxial compression by 6% (0.012 eV). It is predicted that similar heterostructures with an emerging energy gap can be used for various nano- and optoelectronic applications, including Schottky barrier photodetectors.

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Ma, Zechen, Ruifeng Li, Rui Xiong, Yinggan Zhang, Chao Xu, Cuilian Wen, and Baisheng Sa. "InSe/Te van der Waals Heterostructure as a High-Efficiency Solar Cell from Computational Screening." Materials 14, no. 14 (July 6, 2021): 3768. http://dx.doi.org/10.3390/ma14143768.

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Designing the electronic structures of the van der Waals (vdW) heterostructures to obtain high-efficiency solar cells showed a fascinating prospect. In this work, we screened the potential of vdW heterostructures for solar cell application by combining the group III–VI MXA (M = Al, Ga, In and XA = S, Se, Te) and elementary group VI XB (XB = Se, Te) monolayers based on first-principle calculations. The results highlight that InSe/Te vdW heterostructure presents type-II electronic band structure feature with a band gap of 0.88 eV, where tellurene and InSe monolayer are as absorber and window layer, respectively. Interestingly, tellurene has a 1.14 eV direct band gap to produce the photoexcited electron easily. Furthermore, InSe/Te vdW heterostructure shows remarkably light absorption capacities and distinguished maximum power conversion efficiency (PCE) up to 13.39%. Our present study will inspire researchers to design vdW heterostructures for solar cell application in a purposeful way.

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Bu, Wenbo, and Jianlin Shi. "Characterization of Highly Luminescent LaPO4:Eu3+/LaPO4 One-Dimensional Core/Shell Heterostructures." Journal of Nanoscience and Nanotechnology 8, no. 3 (March 1, 2008): 1266–71. http://dx.doi.org/10.1166/jnn.2008.18181.

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Highly luminescent LaPO4:Eu3+/LaPO4 one-dimensional (1D) core/shell heterostructures were successfully synthesized by a mild and simple self-aggregation process under refluxing or hydrothermal conditions. The resulting 1D core/shell heterostructures were characterized using a variety of techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) to demonstrate successful coating by the crystalline LaPO4. In addition, a possible formation mechanism for this core/shell heterostructure was proposed. Finally, the photoluminescence property of the LaPO4:Eu3+/LaPO4 1D core/shell heterostructures was investigated in detail, which illustrates that the core/shell heterostructures remarkably increase the luminescence efficiency because the LaPO4 shells effectively eliminate surface trap-states and suppress the energy quenching in the energy-transfer processes.

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Kooli, Fethi, Yan Liu, Kais Hbaieb, and Rawan Al-Faze. "Preparation and catalytic activities of porous clay heterostructures from aluminium-intercalated clays: effect of Al content." Clay Minerals 52, no. 4 (December 2017): 521–35. http://dx.doi.org/10.1180/claymin.2017.052.4.09.

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AbstractPorous clay heterostructures were prepared from Al-intercalated clays, and they allowed the insertion of Al into the framework of intercalated silica in porous clay heterostructures (PCHs). This method has led to tuneable Al contents within the resulting porous clay heterostructures. X-ray fluorescence confirmed the presence of Al in the intercalated precursors and their derivatives (porous clay heterostructure materials) in various environments, as indicated by 27Al magic-angle spinning nuclear magnetic resonance. The Al porous clay heterostructures exhibited specific surface areas that varied from 743 to 850 m2/g with total acid concentrations which varied from 0.969 to 1.420 mmol of protons/g of material, values which were deduced from the temperature desorption of cyclohexylamine. These acid sites were sufficiently strong to initiate the hydro-isomerization of n-heptane. The catalytic properties of the porous clay heterostructures depended on the Al contents and reached a maximum conversion rate of 50% and an isomer selectivity of 70% at a test reaction temperature of 350°C.

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You, Wenxia, Biyuan Zheng, Zheyuan Xu, Ying Jiang, Chenguang Zhu, Weihao Zheng, Xin Yang, et al. "Strong interfacial coupling in vertical WSe₂/WS₂ heterostructure for high performance photodetection." Applied Physics Letters 120, no. 18 (May 2, 2022): 181108. http://dx.doi.org/10.1063/5.0082101.

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Two-dimensional van der Waals (vdWs) heterostructures have shown great potential in the field of electronic and optoelectronic applications over the recent decade. However, the controlled preparation of high-quality vdWs heterostructures remains a great challenge ascribing to the incompatibility of different material synthesis processes. Here, we report a two-step chemical vapor deposition method for the growth of high quality WS2 on a WSe2 template with a very low temperature of ∼550 °C, where WO3 nanosheets formed in the first step are further employed as the precursor for synthesis of the top WS2 layer in the second step. Such low growth temperatures in the second step also enable the effective protection of bottom WSe2 during the WS2 growth process and, therefore, result in high-quality WSe2/WS2 heterostructures. Photoluminescence characterizations are further conducted, where significant interlayer exciton emission is observed, indicating strong interlayer coupling in the heterostructure. Based on the obtained WSe2/WS2 heterostructure, dual-channel photosensitive devices were further designed and systematically studied, where high photoresponsivity (3 A/W) as well as fast response speed (<1 ms) are obtained. The developed WO3-assisted growth technique would provide an effective reference for the controlled synthesis of high quality vdWs heterostructures and promote further applications in high-performance optoelectronic devices.

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Li, Jiahao, Yanda Ji, Rui Pan, Run Zhao, Ye Yuan, Weiwei Li, and Hao Yang. "Fowler-Nordheim tunneling in β-Ga₂O₃/SrRuO₃ Schottky interfaces." Journal of Physics D: Applied Physics 55, no. 21 (February 25, 2022): 210003. http://dx.doi.org/10.1088/1361-6463/ac5356.

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Abstract Interfaces in heterostructures always emerge as prototype electronic devices with tunable functionality. The fundamental properties of these interfaces can be finely manipulated by epitaxy engineering. Recently, heterostructures based on Ga2O3, an ultra-wide bandgap semiconductor, have been reported for use in high powered device applications. Herein, we will demonstrate a heterostructure of β-Ga2O3/SrRuO3 integrated on c-plane sapphire, where the high density of edge dislocations are evidenced in the heterostructure interfaces. Apart from the dominant Schottky emission mechanism, Fowler-Nordheim tunneling is also revealed by leakage current analysis, which may be ascribed to the edge dislocations at the interfaces. These results boost the basic understanding of ultra-wide bandgap materials and devices.

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Morinson-Negrete, Juan David, César Ortega-López, and Miguel J. Espitia-Rico. "Effects of Mono-Vacancies of Oxygen and Manganese on the Properties of the MnO2/Graphene Heterostructure." Materials 15, no. 8 (April 8, 2022): 2731. http://dx.doi.org/10.3390/ma15082731.

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The effects of the monovacancies of oxygen (VO) and manganese (VMn) on the structural and electronic properties of the 1T–MnO2/graphene heterostructure are investigated, within the framework of density functional theory (DFT). We found that the values of the formation energy for the heterostructure without and with vacancies of VO and VMn were −20.99 meVÅ2 , −32.11meVÅ2, and −20.81 meVÅ2, respectively. The negative values of the formation energy indicate that the three heterostructures are energetically stable and that they could be grown in the experiment (exothermic processes). Additionally, it was found that the presence of monovacancies of VO and VMn in the heterostructure induce: (a) a slight decrease in the interlayer separation distance in the 1T–MnO2/graphene heterostructure of ~0.13% and ~1.41%, respectively, and (b) a contraction of the (Mn−O) bond length of the neighboring atoms of the VO and VMn monovacancies of ~2.34% and ~6.83%, respectively. Calculations of the Bader charge for the heterostructure without and with VO and VMn monovacancies show that these monovacancies induce significant changes in the charge of the first-neighbor atoms of the VO and VMn vacancies, generating chemically active sites (locales) that could favor the adsorption of external atoms and molecules. From the analysis of the density of state and the structure of the bands, we found that the graphene conserves the Dirac cone in the heterostructure with or without vacancies, while the 1T–MnO2 monolayer in the heterostructures without and with VO monovacancies exhibits half-metallic and magnetic behavior. These properties mainly come from the hybridization of the 3d–Mn and 2p–O states. In both cases, the heterostructure possesses a magnetic moment of 3.00 μβ/Mn. From this behavior, it can be inferred the heterostructures with and without VO monovacancies could be used in spintronics.

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HAN, S. M., S. Y. KIM, D. C. CHOO, J. I. JUNG, T. W. KIM, K. H. YOO, Y. H. JO, et al. "ELECTRONIC PARAMETER AND SUBBAND STRUCTURE VARIATIONS DUE TO AN EMBEDDED AlN POTENTIAL BARRIER LAYER IN Al0.3Ga0.7N/GaN HETEROSTRUCTURES." Surface Review and Letters 14, no. 04 (August 2007): 807–11. http://dx.doi.org/10.1142/s0218625x07010305.

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Carrier density of a two-dimensional electron gas (2DEG) in Al 0.3 Ga 0.7 N / GaN and Al 0.3 Ga 0.7 N / AlN / GaN heterostructures was investigated by performing Shubnikov-de Haas (SdH) measurements. The angular-dependent SdH measurements and the fast Fourier transformation results for the SdH data indicated 2DEG occupation of one subband in the triangular potential wells. The carrier densities of the 2DEGs in the Al 0.3 Ga 0.7 N / AlN / GaN and the Al 0.3 Ga 0.7 N / GaN heterostructures at 1.5 K, determined from the SdH data, were 1.28 × 1013 and 1.12 × 1013 cm-2, respectively. The electron carrier density of the 2DEG in the Al 0.3 Ga 0.7 N / GaN heterostructure with an AlN embedded potential barrier layer was larger than that in the Al 0.3 Ga 0.7 N / GaN heterostructure. The electronic subband energies, the wave functions, and the Fermi energies in the Al 0.3 Ga 0.7 N / AlN / GaN and Al 0.3 Ga 0.7 N / GaN heterostructures were calculated by using a self-consistent method taking into account spontaneous and piezoelectric polarizations.

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Xiang, Rong, Taiki Inoue, Yongjia Zheng, Akihito Kumamoto, Yang Qian, Yuta Sato, Ming Liu, et al. "One-dimensional van der Waals heterostructures." Science 367, no. 6477 (January 30, 2020): 537–42. http://dx.doi.org/10.1126/science.aaz2570.

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We present the experimental synthesis of one-dimensional (1D) van der Waals heterostructures, a class of materials where different atomic layers are coaxially stacked. We demonstrate the growth of single-crystal layers of hexagonal boron nitride (BN) and molybdenum disulfide (MoS2) crystals on single-walled carbon nanotubes (SWCNTs). For the latter, larger-diameter nanotubes that overcome strain effect were more readily synthesized. We also report a 5-nanometer–diameter heterostructure consisting of an inner SWCNT, a middle three-layer BN nanotube, and an outer MoS2 nanotube. Electron diffraction verifies that all shells in the heterostructures are single crystals. This work suggests that all of the materials in the current 2D library could be rolled into their 1D counterparts and a plethora of function-designable 1D heterostructures could be realized.

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Albarakati, Sultan, Cheng Tan, Zhong-Jia Chen, James G. Partridge, Guolin Zheng, Lawrence Farrar, Edwin L. H. Mayes, et al. "Antisymmetric magnetoresistance in van der Waals Fe3GeTe2/graphite/Fe3GeTe2 trilayer heterostructures." Science Advances 5, no. 7 (July 2019): eaaw0409. http://dx.doi.org/10.1126/sciadv.aaw0409.

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With no requirements for lattice matching, van der Waals (vdW) ferromagnetic materials are rapidly establishing themselves as effective building blocks for next-generation spintronic devices. We report a hitherto rarely seen antisymmetric magnetoresistance (MR) effect in vdW heterostructured Fe3GeTe2 (FGT)/graphite/FGT devices. Unlike conventional giant MR (GMR), which is characterized by two resistance states, the MR in these vdW heterostructures features distinct high-, intermediate-, and low-resistance states. This unique characteristic is suggestive of underlying physical mechanisms that differ from those observed before. After theoretical calculations, the three-resistance behavior was attributed to a spin momentum locking induced spin-polarized current at the graphite/FGT interface. Our work reveals that ferromagnetic heterostructures assembled from vdW materials can exhibit substantially different properties to those exhibited by similar heterostructures grown in vacuum. Hence, it highlights the potential for new physics and new spintronic applications to be discovered using vdW heterostructures.

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Езубченко, И. С., М. Я. Черных, П. А. Перминов, Ю. В. Грищенко, И. Н. Трунькин, И. А. Черных, and М. Л. Занавескин. "Особенности роста гетероструктур нитрида галлия на подложках кремния: управляемая пластическая деформация." Письма в журнал технической физики 47, no. 14 (2021): 26. http://dx.doi.org/10.21883/pjtf.2021.14.51183.18766.

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Gallium nitride heterostructures were grown on silicon substrates by metalorganic chemical vapour deposition. Substrate plastic deformations that occur during the growth process with the effective compressive stresses accumulation in the film were observed at temperatures of 930oC-975oC. An approach of silicon controlled plastic deformation by high-temperature annealing combined with the in situ SiNx layer growth after heterostructure epitaxy is proposed. This approach would simplify optimization of the gallium nitride heterostructures architecture for various technological tasks.

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Han, Tao, Hongxia Liu, Shulong Wang, Shupeng Chen, Kun Yang, and Zhandong Li. "Synthesis and Spectral Characteristics Investigation of the 2D-2D vdWs Heterostructure Materials." International Journal of Molecular Sciences 22, no. 3 (January 27, 2021): 1246. http://dx.doi.org/10.3390/ijms22031246.

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Due to the attractive optical and electrical properties, van der Waals (vdWs) heterostructures constructed from the different two-dimensional materials have received widespread attention. Here, MoS2/h-BN, MoS2/graphene, WS2/h-BN, and WS2/graphene vdWs heterostructures are successfully prepared by the CVD and wet transfer methods. The distribution, Raman and photoluminescence (PL) spectra of the above prepared heterostructure samples can be respectively observed and tested by optical microscopy and Raman spectrometry, which can be used to study their growth mechanisms and optical properties. Meanwhile, the uniformity and composition distribution of heterostructure films can also be analyzed by the Raman and PL spectra. The internal mechanism of Raman and PL spectral changes can be explained by comparing and analyzing the PL and Raman spectra of the junction and non-junction regions between 2D-2D vdWs heterostructure materials, and the effect of laser power on the optical properties of heterostructure materials can also be analyzed. These heterostructure materials exhibit novel and unique optical characteristics at the stacking or junction, which can provide a reliable experimental basis for the preparation of suitable TMDs heterostructure materials with excellent performance.

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Qian, Hao-Zhi, Bo Wang, Meng-Ting Liu, Nan-Nan Zhao, Zheng-Hua Wang, and Yin Peng. "Unique 1D/2D Bi2O2CO3 nanorod-Bi2WO6 nanosheet heterostructure: synthesis and photocatalytic performance." CrystEngComm 23, no. 35 (2021): 6128–36. http://dx.doi.org/10.1039/d1ce00684c.

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A novel 1D/2D Bi2O2CO3–Bi2WO6 heterostructure was synthesized by high temperature calcination. These 1D/2D Bi2O2CO3–Bi2WO6 heterostructures displayed an outstanding photocatalytic activity to degrade organic compounds.

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Emeline, Alexei V., Aida V. Rudakova, Ruslan V. Mikhaylov, Kirill M. Bulanin, and Detlef W. Bahnemann. "Photoactive Heterostructures: How They Are Made and Explored." Catalysts 11, no. 2 (February 23, 2021): 294. http://dx.doi.org/10.3390/catal11020294.

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In our review we consider the results on the development and exploration of heterostructured photoactive materials with major attention focused on what are the better ways to form this type of materials and how to explore them correctly. Regardless of what type of heterostructure, metal–semiconductor or semiconductor–semiconductor, is formed, its functionality strongly depends on the quality of heterojunction. In turn, it depends on the selection of the heterostructure components (their chemical and physical properties) and on the proper choice of the synthesis method. Several examples of the different approaches such as in situ and ex situ, bottom-up and top-down, are reviewed. At the same time, even if the synthesis of heterostructured photoactive materials seems to be successful, strong experimental physical evidence demonstrating true heterojunction formation are required. A possibility for obtaining such evidence using different physical techniques is discussed. Particularly, it is demonstrated that the ability of optical spectroscopy to study heterostructured materials is in fact very limited. At the same time, such experimental techniques as high-resolution transmission electron microscopy (HRTEM) and electrophysical methods (work function measurements and impedance spectroscopy) present a true signature of heterojunction formation. Therefore, whatever the purpose of heterostructure formation and studies is, the application of HRTEM and electrophysical methods is necessary to confirm that formation of the heterojunction was successful.

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Li, Mengwei, Teng Zhang, Pengcheng Wang, Minghao Li, Junqiang Wang, and Zewen Liu. "Temperature Characteristics of a Pressure Sensor Based on BN/Graphene/BN Heterostructure." Sensors 19, no. 10 (May 14, 2019): 2223. http://dx.doi.org/10.3390/s19102223.

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Temperature is a significant factor in the application of graphene-based pressure sensors. The influence of temperature on graphene pressure sensors is twofold: an increase in temperature causes the substrates of graphene pressure sensors to thermally expand, and thus, the graphene membrane is stretched, leading to an increase in the device resistance; an increase in temperature also causes a change in the graphene electrophonon coupling, resulting in a decrease in device resistance. To investigate which effect dominates the influence of temperature on the pressure sensor based on the graphene–boron nitride (BN) heterostructure proposed in our previous work, the temperature characteristics of two BN/graphene/BN heterostructures with and without a microcavity beneath them were analyzed in the temperature range 30–150 °C. Experimental results showed that the resistance of the BN/graphene/BN heterostructure with a microcavity increased with the increase in temperature, and the temperature coefficient was up to 0.25%°C−1, indicating the considerable influence of thermal expansion in such devices. In contrast, with an increase in temperature, the resistance of the BN/graphene/BN heterostructure without a microcavity decreased with a temperature coefficient of −0.16%°C−1. The linearity of the resistance change rate (ΔR/R)–temperature curve of the BN/graphene/BN heterostructure without a microcavity was better than that of the BN/graphene/BN heterostructure with a microcavity. These results indicate that the influence of temperature on the pressure sensors based on BN/graphene/BN heterostructures should be considered, especially for devices with pressure microcavities. BN/graphene/BN heterostructures without microcavities can be used as high-performance temperature sensors.

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Guha, Puspendu, Joon Young Park, Janghyun Jo, Yunyeong Chang, Hyeonhu Bae, Rajendra Kumar Saroj, Hoonkyung Lee, Miyoung Kim, and Gyu-Chul Yi. "Molecular beam epitaxial growth of Sb₂Te₃–Bi₂Te₃ lateral heterostructures." 2D Materials 9, no. 2 (January 31, 2022): 025006. http://dx.doi.org/10.1088/2053-1583/ac421a.

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Abstract We report on heteroepitaxial growth of Sb2Te3–Bi2Te3 lateral heterostructures using molecular beam epitaxy. The lateral heterostructures were fabricated by growing Bi2Te3 islands of hexagonal or triangular nanostructures with a typical size of several 100 nm and thickness of ∼15 nm on graphene substrates and Sb2Te3 laterally on the side facets of the nanostructures. Multiple-step processes with different growth temperatures were employed to grow the lateral heterostructures. Electron microscopy techniques indicate that the inner region is Bi2Te3 and the outer Sb2Te3 was formed laterally on the graphene in an epitaxial manner. The interface between Bi2Te3 and Sb2Te3 from planar and cross-sectional views was studied by the aberration-corrected (C s-corrected) high-angle annular dark-field scanning transmission electron microscope technique. The cross-sectional electron microscopy investigation shows no wetting layer of Sb2Te3 on Bi2Te3, corroborating perfect lateral heterostructure formation. In addition, we investigated the topological properties of Sb2Te3–Bi2Te3 lateral heterostructures using first-principles calculations.

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Liang, Yuan-Chang, and Yu-Wei Hsu. "Enhanced Sensing Ability of Brush-Like Fe2O3-ZnO Nanostructures towards NO2 Gas via Manipulating Material Synergistic Effect." International Journal of Molecular Sciences 22, no. 13 (June 26, 2021): 6884. http://dx.doi.org/10.3390/ijms22136884.

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Brush-like α-Fe2O3–ZnO heterostructures were synthesized through a sputtering ZnO seed-assisted hydrothermal growth method. The resulting heterostructures consisted of α-Fe2O3 rod templates and ZnO branched crystals with an average diameter of approximately 12 nm and length of 25 nm. The gas-sensing results demonstrated that the α-Fe2O3–ZnO heterostructure-based sensor exhibited excellent sensitivity, selectivity, and stability toward low-concentration NO2 gas at an optimal temperature of 300 °C. The α-Fe2O3–ZnO sensor, in particular, demonstrated substantially higher sensitivity compared with pristine α-Fe2O3, along with faster response and recovery speeds under similar test conditions. An appropriate material synergic effect accounts for the considerable enhancement in the NO2 gas-sensing performance of the α-Fe2O3–ZnO heterostructures.

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Xia, Qing, Deyuan Li, Lanling Zhao, Jun Wang, Yuxin Long, Xue Han, Zhaorui Zhou, et al. "Recent advances in heterostructured cathodic electrocatalysts for non-aqueous Li–O₂ batteries." Chemical Science 13, no. 10 (2022): 2841–56. http://dx.doi.org/10.1039/d1sc05781b.

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The structure–function relationships between heterostructures and their catalytic properties were discussed in detail, and the challenges and improvement strategies for heterostructure based cathodes towards Li–O2 catalysis were also summarized.

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Panthi, Gopal, and Mira Park. "Electrospun Carbon Nanofibers Decorated with Ag3PO4 Nanoparticles: Visible-Light-Driven Photocatalyst for the Photodegradation of Methylene Blue." Photochem 1, no. 3 (October 10, 2021): 345–57. http://dx.doi.org/10.3390/photochem1030022.

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For the first time, heterostructures of electrospun carbon nanofibers decorated with Ag3PO4 nanoparticles (Ag3PO4/CNFs) were successfully fabricated by the combination of simple and versatile electrospinning technique followed by carbonization and incorporation of Ag3PO4 nanoparticles via colloidal and precipitation synthesis approaches. The as-fabricated heterostructures were characterized by FESEM with EDS, XRD, TEM with HRTEM, FTIR and UV-vis diffuse reflectance spectroscopy. Experimental results revealed that the heterostructure obtained by colloidal synthesis approach (Ag3PO4/CNFs-1) was decorated with small-sized (~20 nm) and uniformly distributed Ag3PO4 nanoparticles on the surface of CNFs without any evident agglomeration, while in the heterostructure obtained by the precipitation synthesis approach (Ag3PO4/CNFs-2), CNFs were decorated with agglomerated and bigger-sized Ag3PO4 nanoparticles. The visible-light-driven photocatalytic investigation signified that the Ag3PO4/CNFs-1 heterostructure can exhibit higher performance towards the photodegradation of MB dye solution compared to the Ag3PO4/CNFs-2 heterostructure, which could be attributed to the synergistic effect between the uniformity and small size of Ag3PO4 nanoparticles and CNFs that can serve as a conductivity network to prevent the recombination of charge carriers. Moreover, the mechanism of the photocatalytic activity as-prepared heterostructure is proposed.

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Journal articles on the topic 'Heterostructures Heterostructures'

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