Rozprawy doktorskie na temat „Nano-Crystalline Silicon”

Cette thèse s’intéresse à l’analyse de cellules silicium cristallin à l’échelle nanométrique, à l’aide de techniques de microscopie à sonde locale (SPM). En particulier, nous avons choisi d’analyser les propriétés électriques à l’échelle locale, grâce à deux techniques SPM : la microcopie à sonde de Kelvin (KPFM) et la microscopie à force atomique à sonde conductrice (CP-AFM).Tout d’abord, nous présentons les forces et faiblesses de ces deux techniques, comparées à la microscopie électronique, qui permet également d’analyser les propriétés électrique à l’échelle nanométrique. Cette comparaison approfondie nous permet d’identifier des mesures où le KPFM et le CP-AFM sont particulièrement adéquat et peuvent apporter de la valeur. Ces mesures sont divisées en deux catégories : les analyses matériaux et les analyses dispositifs.Ensuite, nous nous focalisons sur les analyses matériaux à l’échelle nanométrique. Nous présentons d’abord des mesures de dopage à l’échelle nanométrique, à l’aide d’une technique avancée de CP-AFM, appelée Resiscope. Nous montrons que cette technique peut détecter des changements de dopage dans la gamme 1015 à 1020 atomes.cm-3, avec une résolution nanométrique et un bon ratio signal/bruit. Puis, nous présentons des mesures de durée de décroissance sur des wafers silicium cristallin passivés. Les mesures sont réalisées sur la tranche non-passivée des échantillons. Nous montrons que, même si la tranche n’est pas passivée, les durées de décroissance obtenue par KPFM ont une bonne corrélation avec les temps de vie des wafers mesurées par décroissance de la photoconductivité détectée par micro-ondes.Par la suite, nous nous concentrons sur les analyses dispositif. A l’aide du KPFM, nous analysons deux types de cellules solaires silicium cristallin : les cellules solaires silicium épitaxié (epi-Si) et les cellules solaires hétérojonctions à contact arrière (IBC). En particulier, nous nous focalisons sur l’analyse de dispositifs en condition d’opération. Nous étudions d’abord l’influence de la tension électrique appliquée et nous montrons que les effets de résistance et de diode peuvent être détectés à l’échelle nanométrique. Les mesures de KPFM sont comparées aux mesures de microscopie électronique à balayage (SEM) dans les mêmes conditions, puisque le SEM est aussi sensible au potentiel de surface. Nous montrons que les mesures KPFM sur la tranche de cellules solaires epi-Si peuvent permettre d’étudier les changements de champ électrique avec la tension électrique appliquée. De plus, si la tension électrique est modulée en fréquence, nous montrons que des mesures de temps de vie peuvent être effectuées à l’échelle locale sur la tranche de cellules solaires epi-Si, ce qui peut permettre de détecter les interfaces limitantes. Puis, nous étudions l’influence de l’illumination sur les mesures KPFM et CP-AFM. Nous effectuons des mesures sur la tranche de cellules epi-Si sous différentes valeurs d’intensité et longueurs d’onde d’illumination. Nous montrons une bonne sensibilité des mesures KPFM à l’illumination. Cependant, nous montrons que pour différentes longueurs d’onde, à tension de circuit ouvert fixé, nos mesures ne sont pas corrélées avec les mesures de rendement quantique interne, comme nous le pensions.Enfin, nous résumons notre travail dans un tableau qui représente les forces et faiblesses des techniques pour les différentes mesures d’intérêt exposées précédemment. A partir de ce tableau, nous imaginons un setup de microscopie « idéal » qui permette d’analyser les cellules solaires de manière fiable, versatile et précise. Pour finir, nous proposons des mesures d’intérêt qui pourraient être réalisées avec ce setup « idéal »
This thesis focuses on the investigation of crystalline silicon solar cells at the nano-scale using scanning probe microscopy (SPM) techniques. In particular, we chose to investigate electrical properties at the nano-scale using two SPM techniques: Kelvin Probe Force Microscopy (KPFM) and Conducting Probe Atomic Force Microscopy (CP-AFM).First, we highlight the strengths and weaknesses of both these techniques compared to electron microscopy techniques, which can also help investigate electrical properties at the nano-scale. This comprehensive comparison enables to identify measurements where KPFM and CP-AFM are particularly adequate. These measurements are divided in two categories: material investigation and devices investigation.Then, we focus on materials investigation at the nano-scale using SPM techniques. We first present doping measurements at the nano-scale using an advanced CP-AFM technique called Resiscope. We prove that this technique could detect doping changes in the range 1015 and 1020 atoms.cm-3 with a nano-scale resolution and a high signal/noise ratio. Then, we highlight decay time measurements on passivated crystalline silicon wafers using KPFM. Measurements are performed on the unpassivated cross-section. We show that, even though the cross-section is not passivated, decay times measurements obtained with KPFM are in good agreement with lifetimes measured by microwave photoconductivity decay.Subsequently, we focus on device measurements. Using KPFM, we investigate two different crystalline silicon solar cell architectures: epitaxial silicon (epi-Si) solar cells and interdigitated back contact (IBC) heterojunction solar cells. In particular, we focus on measurements on devices under operating conditions. We first study the influence of the applied electrical bias. We study the sensitivity of surface potential to electrical bias and we show that diode and resistance effects can be detected at the nano-scale. KPFM measurements are compared to scanning electron microscopy (SEM) measurements in the same conditions since SEM is also sensitive to surface potential. We show that KPFM measurements on the cross-section of epi-Si solar cells can help detect electric field changes with electrical bias. Besides, if the electrical bias is frequency modulated, we show that lifetime measurements can be performed on the cross-section of epi-Si solar cells and can help detect limiting interfaces and layers. Then, we study the influence of illumination on KPFM and CP-AFM measurements. We perform photovoltage and photocurrent measurements on the cross-section of epi-Si solar under different values of illumination intensity and illumination wavelength. We show a good sensitivity of KPFM measurements to illumination. However, we show that measurements for different wavelengths at a given open circuit voltage, are not correlated with the internal quantum efficiency, as we could have expected.Finally, we summarize our work in a table showing the impact of strengths and weaknesses of the techniques for the different measurements highlighted. From this table, we imagine an “ideal” microscopy setup to investigate crystalline silicon solar cells in a reliable, versatile and accurate way. We propose investigations of interest that could be carried out using this “ideal” setup

In this thesis, we compared electrical performance and stability of a novel nanocrystalline Si (nc-Si) thin film phototransistor (TFT) phototransistor and a regular amorphous silicon (a-Si:H) TFT phototransistor for large area imaging applications. The electrical performance parameters of nc-Si TFT phototransistor were extracted from the electrical (current-voltage) testing in dark and under illumination. The field-effect mobility is found to be around 1.2 cm2V-1s-1, the threshold voltage around 3.9V and the sub-threshold voltage slope around 0.47V/Dec. Optical properties of nc-Si TFT phototransistor have been evaluated under the green light illumination in the range of 1014 – 1017 lum, and the photocurrent gain and the external quantum efficiency were extracted from the experimental results. By comparing the results with those for a-Si:H TFTs measured under the same conditions, we found that nc-Si TFT has higher photo current gain under low illumination intensity, 5 ×1014 to 7 ×1015 lum. This thesis shows the relations bewteen the photo current gain, the external quantum efficiency, TFT drain and TFT gate bias; the photo current gain and the external quantum efficiency can be controlled by the Vds and the Vgs.

碩士
元智大學
光電工程研究所
99
Ｗe successfully form self-assemble ,close-packed and monolayer polystyrene nanospheres on the surface of silicon wafers, by employing simpley and cost-effectively spin-coating method. These nanospheres are used as sacrificial etching masks for reactive ion etching (RIE) process to fabricate different profile nano-arrays characterized as broadband antireflective and effective carrier collection structures for enhancing light harvesting of crystalline Si-based solar cells. Conventional antireflection layers were usually fabricated by depositing a single or multiple layers with restricted thickness and material selection on the silicon solar cells. However, the conventional method exhibited several drawbacks : 1. The stack of layers serve narrow-band antireflective properties. 2. Thermal mismatch and instability of the thin-film stacks have been the major obstacles to achieve broadband antireflection coatings. 3. Selection of materials with proper dielectric constants is difficult. According to the previous studies, the surface nano-arrays were reported to exhibit better broadband antireflective characteristics than the multiple antireflective layers, it opens up exciting opportunities for photovoltaic devices to further improve performance. In this project, we intend to demonstrate a high performance, large area Si solar cells by integrateing the antireflective nanostructure, We utilized rigorous coupled wave analysis (RCWA) method to calculate the reflectance of the nanostructured solar cells and desire to further optimize the light harvesting of the cells. In addition, implementation of the nanostructure will be conducted on silicon-based solar cells to reduce the broadband reflectance. After the RIE process, the samples with trapezoid structure were treated by dipping in HF:HNO3:H2O (2:48:50) solution to remove the damaged layer. This step is called defect removal etching (DRE). Not only the reflectance were reduced but also the lifetime was increased after DRE process. The data of lifetime and reflectance were input to APSYS simulator to calculate the short circuit current, open circuit voltage, and power conversion effeciency. The effeciency of trapezoid structures with DRE treatment achieve 15.51%, which shows an 16.53% compared to flat Si solar cells. We believe the trapezoid structures with DRE treatment are excellent anti-reflectance structures, which are promising candidates to realize the low-cost, high-efficiency solar cells.

Silicon-based nanostructures are essential building blocks for nanoelectronic devices and nano-electromechanical systems (NEMS). As the silicon device size continues to scale down, the surface to volume ratio becomes larger, rendering the properties of surfaces and interfaces more important for improving the properties of the nano-devices and systems. One of those properties is the friction, which is important in controlling the functionality and reliability of the nano-device and systems. The goal of this dissertation is to investigate the deformation and friction behaviors of single crystalline silicon nanolines (SiNLs) using nanoindentation techniques. Following an introduction and a summary of the theoretical background of contact friction in Chapters 1 and 2, the results of this thesis are presented in three chapters. In Chapter 3, the fabrication of the silicon nanolines is described. The fabrication method yielded high-quality single-crystals with line width ranging from 30nm to 90nm and height to width aspect ratio ranging from 10 to 25. These SiNL structures have properties and dimensions well suited for the study of the mechanical and friction behaviors at the nanoscale. In Chapter 4, we describe the study of the mechanical properties of SiNLs using the nanoindentation method. The loading-displacement curves show that the critical load to induce the buckling of the SiNLs can be correlated to the contact friction and geometry of SiNLs. A map was built as a guideline to describe the selection of buckling modes. The map was divided into three regions where different regions correlate to different buckling modes including Mode I, Mode II and slidingbending of SiNLs. In Chapter 5, we describe the study of the contact friction of the SiNL structures. The friction coefficient at the contact was extracted from the loaddisplacement curves. Subsequently, the frictional shear stress was evaluated. In addition, the effect of the interface between the indenter and SiNLs was investigated using SiNLs with surfaces coated by a thin silicon dioxide or chromium film. The material of the interface was found to influence significantly the contact friction and its behavior. Cyclic loading-unloading experiments showed the friction coefficient dramatically changed after only a few loading cycles, indicating the contact history is important in controlling the friction behaviors of SiNLs at nanoscales. This thesis is concluded with a summary of the results and proposed future studies.
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碩士
國立臺灣科技大學
光電工程研究所
101
In this dissertation, Nano/Micro crystalline diamond were fabricated on different silicon-based structures to study the effect on the field emission properties. NCD and MCD were deposited on Planar-Si, Pyramid-Si and SiNWs/Pyramid-Si by microwave plasma chemical vapor deposition system. The surface morphologies of diamond were characterized by the field emission scanning electron microscopy. The characterizations of diamond were analyzed by Raman, XPS and AFM to show the quality, the sp3/sp2 ratio and average roughness of diamond, respectively. It is found that the turn on electric field of NCD/SiNWs/Pyramid-Si field emission cathode is lower (3.11 V/μm) through ultrasonication pretreatment than other structures such as NCD/Planar-Si (4.8 V/μm) and NCD/Pyramid-Si (4.35 V/μm). And the lower turn on electric field NCD/SiNWs/Pyramid-Si (3.2 V/μm) through rub and ultrasonication pretreatments than other structure such as NCD/Pyramid-Si (3.9 V/μm). While using C10H16 and ethylene glycol as seeds layer to deposite MCD on Planar-Si and Pyramid structures, the turn on field improved from 3.86 V/μm of MCD/Planar-Si to 3.15 V/μm of MCD/Pyramid-Si. And 4.5 V/μm of MCD/Planar-Si to 2.9 V/μm of MCD/Pyramid-Si by using C10H16 and diethylene glycol as seeds layer. Keyword: NCD, SiNWs, Pyramid

碩士
大同大學
光電工程研究所
97
Nano-crystalline silicon has been deposited on glass and plastic substrates by direct vacuum arc system at room to cryogenic temperature(77 K). Solid silicon wafer source were amount on both anode and cathode to be the electrodes which were highly doped single crystal silicon wafer(0.005 Ω/cm). It is suitable for deposited thin films on flexible substrate due to low deposition temperature. Silicon films were characterized by Raman spectroscopy、x-ray diffraction (XRD)、tunneling electron microscope (TEM) and scanning electron microscope (SEM). The result revealed that the crystalline structure embedded in amorphous matrix. High-resolution transmission electron microscopy (HRTEM) was used for direct analyzing the particle where the fully crystallized structure were inert the particles and these particles were random distributed over the substrate. The crystalline volume fraction were calculated from Raman spectrum and it showed the values between 0~92 ％. The impurity concentration was measured by SIMS, that the P-type and N-type impurity was permeated simultaneously into the film during the deposition without additional doping process, thus P-N junction could be achieved. Nano-crystalline silicon has higher electron mobility and more stability against prolong light exposure than amorphous silicon. According to our research, the opto-electronic effect were not obviously, we assume that a large number of defects existed in the films. Compared to CVD process, arc discharge system has the advantages of low cost, less environment pollution and non-dangerous of processing. Such research has not yet been observed. Low temperature deposited nano-crystalline silicon thin film has attracted much attention due to applicable on low-cost substrates, like glass and flexible plastic substrate. Key words: Direct vacuum arc, Flexible substrate, crystalline volume fraction.

博士
國立成功大學
航空太空工程學系碩博士班
101
The objective of the current study is to develop and fabricate silicon based crystalline materials in order to make into photovoltaic (PV) solar cells. The current study of silicon films for PV applications includes two different parts based on the individual matrix around the crystalline materials. One of the studies is the development and fabrication of applying silicon quantum dots thin films to crystalline silicon solar cells, the other is the study of hydrogenated microcrystalline silicon thin film solar cells. For characterization of silicon quantum dots films under different process conditions, after deposition of silicon rich nitride layer by the PECVD process a high temperature anneal is adopted so that excessive amount of silicon quantum dots can be precipitates in the silicon rich nitride layer. An optimum condition for the anneal to obtain silicon quantum dots film has been verified through series of tests. In addition, the number of silicon quantum dots within the film can be controlled by varying the mixing ratio of silane and ammonia gas. This variation of silicon quantum density within the film causes different photo response. The conversion efficiency of the solar cell with silicon film embedded with silicon quantum dots can be improved from 5.42% to 6.49%. The other part is development and fabrication of microcrystalline silicon thin film solar cells with intrinsic layer deposited at different hydrogen gas flow, silane flow rate, deposition working pressure and power density at 40.68 MHz with very-high-frequency plasma-enhanced chemical vapor deposition system. As the results of film properties, the increase of hydrogen gas flow or the decrease of silane gas flow can increase the crystalline volume ratio in the films. The efficiency of solar cell made by this thin film increases from 4.54% to5.39% as the crystalline volume ratio in the film increases. However, the efficiency of the solar cell decreases as the crystalline volume ratio becomes too high. The increase in fabrication pressure from 5Torr to 7Torr can lead to notable improvement in cell efficiency from 5.39% to6.39%, but the increase in power density does not have any improvement in cell efficiency. Further improvement of the cell efficiency can be achieved by changing the structure of solar cell, and surface treatment on the p-i surface of the solar cell. It is shown that the diborane gas flush treatment on the p layer can improve the cell efficiency. Besides, replacing microcrystalline p layer with the amorphous p type silicon carbide can substantially improve the solar cell efficiency due to the significant increase in Voc but slight decrease in currents density. The conversion efficiency increases from 6.39% to8.35%.

碩士
元智大學
先進能源研究所
99
In this study, the silicon nano-crystals were embedded into amorphous silicon thin films, leading to an increase in optical band gap due to the quantum confinement effect. A nc-Si:H film with the band gap of 1.95 eV was obtained by VHF (27.12 MHz) PECVD system and was used as a window layer for p-i-n a-Si:H thin film solar cells. The hetero-junction, p-layer nc-Si:H/i-layer a-Si:H, solar cell demonstrated an open-circuit voltage (Voc) of 0.88 V and a conversion efficiency of greater than 9%. This kind of cell structure has great potential for the development of the a-Si/uc-Si tandem cell and the conversion efficiency is expected to be 11%. In addition, ECR-CVD (microwave frequency: 2.45 GHz) technique is powerful for the deposition of silicon films with high deposition rate. In this study, we attempted to use the system to deposit silicon films. The PECVD process experiences were helpful to give reasonable deposition parameters for ECR-CVD. Finally, we give some suggestions base on the measurement results of the film deposited by ECR-CVD.

碩士
國立金門大學
電子工程學系碩士班
107
There are two topics in this research. One is rareearth ions(Sm3+ , Bi3+；Dy3+；Ce3+, Yb3+) doped Yttrium phosphate (YPO4) were prepared by the chemical co-precipitation method. And then added the surfactants (CTAB、Tween 80、PVP and PEG2000) to reduce the average diameter of phosphors. In the photoluminescence spectra (PL) and photoluminescence excitation spectra (PLE), YPO4: Sm3+, Bi3+、YPO4: Dy3+、1 g PEG2000 assisted YPO4: Dy3+、YPO4: Ce3+, Yb3+ and 1 g CTAB assisted YPO4: Ce3+, Yb3+ have the relative superiority of excitation intensity. Thus, these five kinds of phosphors were the main objects of discussion in this research. Scanning Electron Microscope (SEM) can observe the surfactants effectively reduce the average diameter of phosphors. All X-ray diffractometer (XRD) patterns are similar to the host material - YPO4 and exhibited the tetragonal crystal structure. The other topic is producing nano-composite film implemented onto a single crystalline silicon solar cell to improve the conversion efficiency. The SiO2 colloidal precursor was a preparation for the stoichiometric ratio of Tetraethyl orthosilicate (TEOS), Hydrochloric acid (HCl), Isopropyl alcohol(IPA) and distilled water. Then phosphors were dispersed in the colloidal precursor and the mixture above was coated onto a single crystalline silicon solar cell by spin coater. After coating, the solar cell was dried in the air atmosphere at 30°C for 10 minutes. The data of efficiency shows that can enhance 0.714% with 1 g CTAB assisted YPO4: Ce3+, Yb3+ -based nano-composite film on the solar cell. The Δƞ/ƞbare is up to 5.255%. The result has proved that the conversion efficiency of solar cells can be improved rapidly without any modification of basic cell structure.

Energy is the number one problem facing humanity today. Solar cells can capture and transform clean and abundant solar energy into electricity. However, their efficiency must increase and their material and fabrication costs must decrease in order for them to be considered as a viable alternative to the fossil fuels. This research explores and studies new methods for fabricating silicon micro- and nano-scale structures in an economical way as building blocks for crystalline silicon solar cells to lower their overall manufacturing cost while increasing their overall efficiency. A novel cost-effective approach was proposed and studied for texturing the crystalline silicon using the gas lift effect (GLE). The new proposed method takes advantage of the generated bubbles to create a gas lift effect that increases the surface wetability and removes undesired gas bubbles during the texturing process. This technique requires 50% less chemicals and 60% shorter etching time to achieve the same reflectivity. Modeling and simulation techniques were used to investigate and elucidate the fluid flow patterns inside the silicon texturing system operating under the new GLE approach. The simulation tool validated the correlation of the lower fluid velocity with the reduced surface coverage, uniformity and subsequently less optimal surface reflectivity. Various inlet designs were modeled and evaluated using a simulation tool for optimal performance. The best inlet design was fabricated and tested resulting in the validation of the simulation work and significant improvement in the GLE texturing system performance. Two solar cell devices, one based on the novel GLE texturing approach, and the other based on the conventional method, were designed, fabricated and characterized. The application of the new GLE texturing approach resulted in considerable improvements in overall power efficiency of silicon solar cells without any additional increase to the production cost. Micro and nano structures can enhance optical absorption characteristics and help with providing a more direct path for charge transport to the contacts resulting in an increased overall efficiency. An array of silicon micro-rods with nano-tip was fabricated through a novel low cost multistage approach. The transformation of the pyramid-covered silicon surface to the array of free-standing micro-rods with nano-tip as well as their growth mechanism was investigated. At lower than 80% pyramid coverage, the number of nanostructures dropped dramatically and no nano-structures were obtained at low surface coverage values of less than 50%. Transparent conductive films (TCFs) can be a viable low-cost alternative to the expensive Indium Tin Oxide (ITO) used in solar cells. A novel thermoplastic nanocomposite of copper nanowires and polymethylmethacrylate was developed by solution mixing technique. Thin films of highly conductive nanocomposites were fabricated by solution casting. This investigation demonstrated that the addition of electric conductive nanoscale fibers to a polymer solution at low concentration levels can transform the plastic to highly conductive phase while maintaining an acceptable transparency of about 55%.

碩士
國立中央大學
光機電工程研究所
106
large-scale data analysis of Plasma Enhanced Chemical Vapor Deposition (PECVD) hydrogenated nanocrystalline germanium (nc-Si:H) thin films was investigated by plasma spectroscopy (OES) plasma diagnostics. The effect of hydrogen dilution ratio(R = H_2 / 〖SiH〗_4)on the structure and optical evolution of deposited nc-Si:H films was investigated, and the principle of RF matching network was analyzed. The function of each component of the impedance matching network is studied. The results show that the matching network can maintain high RF coupling efficiency and reduce the reflected power by using variable plasma parameters. This will create more machine knowledge that is being monitored, including OES complex and non-linear machine data. In this paper, an OES-based Crystallization Rate (Health Value) limit is proposed for on-line crystallization rate assessment testing and diagnostics. The crystallinity of the hydrogenated nanocrystalline germanium (nc-Si:H) film has been analyzed and compared. In this work, the method of bias and the combination of more dimensionality reduction methods and principal component analysis (PCA) were studied. The latter algorithm was named as Health Value and was verified in case studies. Including Raman spectroscopy (Raman), Fourier transforms infrared spectroscopy (FTIR), and X-ray diffraction spectroscopy (XRD). The measurement results show that the structural evolution of nc-Si:H can be induced by adjusting the hydrogen dilution ratio (R), mainly from the amorphous state to the nanocrystalline state. In addition, a plasma diagnostic tool using immediate plasma emission spectroscopy (OES) was used to analyze the increased crystallization rate index(H_α^* / 〖SiH〗^*) when the hydrogen dilution ratio (R) was increased and the deposition rate was decreased. Another plasma diagnostic tool for quadrupole mass spectrometry (QMS) (Threshold Ionization Mass Spectrometry (TIMS)) also confirmed that 〖SiH〗_x / 〖SiH〗_4density shows a change in hydrogen input with the trend of 〖SiH〗^* As a leading turning point, TIMS analysis of nc-Si:H film consumes higher methane methane radicals (〖SiH〗_x，x < 4), showing a turning point in the density trend in the nc-Si:H deposition process area, The free radical is SiH^* instead ofSiH_3. The relative density and hydrogen dilution ratio (R = 30-40) can produce an optima hydrogenated nanocrystalline (nc-Si:H).

碩士
大葉大學
醫療器材設計與材料碩士學位學程
107
The original material is silicon slurry, which obtains by cutting the wafer. The solid particles of slurry acquired by preliminary solid-liquid separation and alkalized to form the silica sol, which is the initial material for experimental study. The main goal of this study is to prepare a nano-scale crystalline silica powder from silica sol by simple hydrothermal processes. The preliminary hydrothermal research carried out with the adjustment of pH value of silica sol, hydrothermal reaction temperature and it's’ holding time. After the hydrothermal process, all product powder was cleaned, filtered and dried. Then, the equipment of FE-SEM and XRD applied to examine the morphology and crystalline structure of each parameter powder. In this way, it will explore the change or influence the crystalline structure and product appearance with pH value, temperature or time adjustment. From experimental examining, results show that besides the pH value of the silica sol will obviously affect the appearance and crystalline intensity of the product. At the same time, the change of hydrothermal temperature and holding time are also important factors to influence the characteristics of products. Regardless of the flake-like or granular-shape product, it is a standard α-quartz crystal. Furthermore, the crystalline intensity of the product tends to increase continuously with increasing the holding time. From results also knowing that applying a simple hydrothermal process treating industrial silica sol, the nano-grade crystalline product can obtain successfully.