Low Hydrogen Dilution Research Articles

Effect of Alloy Composition on the Optoelectronic Properties of Hydrogenated Microcrystalline Silicon-Germanium Films Deposited with Various Hydrogen Dilution

Hydrogenated microcrystalline silicon-germanium (μc-Si1-xGex: H) films were fabricated by plasma-enhanced chemical vapor deposition. The influence of hydrogen dilution on the optoelectronic and crystal structural properties of μc-Si1-xGex: H films were investigated upon alloy composition. Under the relatively low hydrogen dilution condition, the Si atoms of films are easier to crystallize than the Ge atoms, and the dark and photo-conductivity decreased with the Ge concentration because of the reduced crystalline volume fraction of the Si atoms (X Si-Si ) and the increased Ge dangling bond density. However, under higher hydrogen dilution condition, crystallization of the Si atoms decreased while crystallization of the Ge atoms increased with Ge incorporation, and the optoelectronic properties were strongly influenced by the defect density and crystallization of Ge atoms in films.

Very low-temperature growth of silicon thin films using chlorinated precursors and optical properties

In this work, the effect of the very low substrate temperature and hydrogen dilution on chemical, structural, and optical properties of polymorphous silicon thin films (pm-Si:H) using dichlorosilane as a silicon gas precursor in the plasma enhanced chemical vapor deposition (PECVD) was analyzed. The films were synthesized at a lower deposition temperature in the range from 60 to 150 °C and two H2 dilutions of 60 and 100 sccm. Hydrogen incorporation in silicon thin films has been studied by Elastic Recoil Detection Analysis (ERDA) and Fourier Transform Infrared Spectroscopy (FTIR). FTIR was also used to verify the chemical stability of the material as a function of oxidation state and hydrogen effusion. The ERDA analysis evidenced that the hydrogen content typically does not exceed 30 at. %, and the lowest value obtained is around 10 at. %. With Raman spectroscopy, the crystalline fraction was obtained in the range of 5–20%, and the average size of the embedded nanocrystals was found to be between 2 and 3 nm, which was cross-checked by High-Resolution Transmission Electron Microscopy (HRTEM). Finally, by UV–Vis spectroscopy, the effective optical band gap of this material has been calculated, and the value was found to be around 1.6 eV (absorber layer) for the samples with 100 sccm of H2 dilution and around 2.2 eV (window layer) for the samples with 60 sccm of H2 dilution. Overall the increase in the substrate temperature resulted a better ordering in the amorphous matrix, whereas, with the increase in the hydrogen dilution an improvement in the structure factor was observed. Suitable properties of the deposited material in the present work could be useful for the development of a thin silicon layer for different silicon solar cell technologies.

The effects of doping type on structural and electrical properties of silicon nanocrystals layers grown by plasma enhanced chemical vapor deposition

The purpose of this paper is to compare the influence of boron and phosphor doping on the optical, structural and electrical properties of hydrogenated amorphous silicon (a-Si:H) thin films elaborated at low radiofrequency power and low hydrogen dilution. Structural properties of deposited films were investigated by scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GI-XRD) and Raman spectroscopy. The SEM analysis shows that the best homogeneity is observed in the layer doped with low diborane flow rate. Reflectance, XRD and Raman measurements show that the doping of thin films induces the formation of nanocrystallites (nc-Si) embedded in the amorphous matrix with higher density in the phosphorus-doped layers compared to those of boron-doped one. The temperature dependent electrical properties of Au/a-Si:H Schottky diodes were investigated using current–voltage characteristics (I–V), admittance spectroscopy technique and capacitance–voltage characteristics [C(V)] in the temperature range of 100–400 K. From the I–V analyses based on thermionic emission (TE) theory we notice the heterogeneity of the barrier height of the Schottky diodes. From the electrical conductivity measurements, we plotted the evolution of the logarithm of the conductivity σ·T as a function of 1000/T. Activation energies \({\text{E}}_{{\text{a}}}^{{{\text{Low}}}}\) and \({\text{E}}_{{\text{a}}}^{{{\text{High}}}}\) of the samples in low and high temperature ranges respectively are estimated. The decrease of \({\text{E}}_{{\text{a}}}^{{{\text{Low}}}}\) with increasing boron flow rate is attributed to an increase in the density of the traps in the band gap of silicon. On the other hand, we found that \({\text{E}}_{{\text{a}}}^{{{\text{High}}}}\)increases when the flow rate of boron increases and decreases when the flow rate of phosphorus increases. We attributed these behaviors to the increase in the crystallinity of the n-type layers and to the presence of a deep defect in the p-type layers. C−2(V) plots show the presence of two linear regions. We found that the response of the nanocrystalline phase becomes more pronounced at high doping flow rate. Optical, structural and electrical measurements confirmed that the type and the density of doping are important parameters that influence the electrical properties of nc-Si:H Schottky diodes.

Time-resolved, nonequilibrium carrier dynamics in Si-on-glass thin films for photovoltaic cells

A femtosecond pump–probe spectroscopy method was used to characterize the growth process and transport properties of amorphous silicon-on-glass, thin films, intended as absorbers for photovoltaic cells. We collected normalized transmissivity change (ΔT/T) waveforms and interpreted them using a comprehensive three-rate equation electron trapping and recombination model. Optically excited ∼300–500 nm thick Si films exhibited a bi-exponential carrier relaxation with the characteristic times varying from picoseconds to nanoseconds depending on the film growth process. From our comprehensive trapping model, we could determine that for doped and intrinsic films with very low hydrogen dilution the dominant relaxation mode was carrier trapping; while for intrinsic films with large hydrogen content and some texture, it was the standard electron–phonon cooling. In both cases, the initial nonequilibrium relaxation was followed by Shockley–Read–Hall recombination. An excellent fit between the model and the ΔT/T experimental transients was obtained and a correlation between the Si film growth process, its hydrogen content, and the associated trap concentration was demonstrated.

A-SixC1−x:H thin films with subnanometer surface roughness for biological applications

The characterization of a-SixC1−x:H thin films by plasma-enhanced chemical vapor deposition with high hydrogen dilution for biological applications is addressed. A root mean square roughness less than 1 nm was measured via atomic force microscopy for an area of 25 μm2. Structural analysis was done using Fourier transform infrared spectroscopy in the middle infrared region. It was found that under the deposition conditions, the formation of Si–C bonds is promoted. Electrical dark conductivity measurements were performed to evaluate the effect of high hydrogen dilution and to find the relation between carrier transport properties and the structural arrangement. Conductivities of the order of 10−7 to 10−9 S/cm at room temperature for methane–silane gas flow ratio from 0.35 to 0.85 were achieved, respectively. UV-visible spectra were used to obtain the optical band gap and the Tauc parameter. Optical band gap as wide as 3.55 eV was achieved in the regime of high carbon incorporation. Accordingly, deposition under low power density and high hydrogen dilution reduces the roughness, improves the structure of the network, and stabilizes the film properties as a greater percentage of carbon is incorporated. The biofunctionalization of a-SixC1−x:H surfaces with NH2-terminated self-assembled monolayers was obtained through silanization with 3-aminopropyltrimethoxysilane. This knowledge opens a window for the inclusion of these a-SixC1−x:H thin films in devices such as biosensors.

Precise control over oxygen impurities in nano-crystalline silicon thin film processed with a low hydrogen dilution gas system at near room temperature

An atmosphere highly diluted with hydrogen is essential to increase the crystal fraction during formation of hydrogenated nano-crystalline (nc) or micro-crystalline (μc) silicon thin films via chemical vapor deposition (CVD). This hydrogen-rich process, however, hinders the ability for the material to find adequate use in micro-electronic devices due to contamination that results in oxygen-related problems such as donor-like doping, defect creation, or passivation. The use of neutral beam assisted chemical vapor deposition (NBaCVD), with a low hydrogen ratio (R = H2/SiH4) of 4, successfully deposits a highly-crystallized nc-silicon (HC nc-Si) thin film (TF) at near room temperature (<80 °C) and effectively reduces oxygen contamination by as much as 100 times when compared to conventional plasma enhanced CVD. During the formation of HC nc-Si TF via NBaCVD, energetic hydrogen atoms directly react with oxygen atoms near the surface of the nc-Si TF and remove the oxygen impurities. This is a completely different mechanism from the hydrogen-enhanced oxygen diffusion model. This technology meets the recent requirements of a high deposition rate and low temperature necessary for flexible electronics.

Low temperature growth of highly conductive boron-doped germanium thin films by electron cyclotron resonance chemical vapor deposition

The effect of the doping ratio (B2H6/GeH4) on the structural and electrical properties of boron doped hydrogenated germanium films deposited by the electron cyclotron resonance chemical vapor deposition process has been investigated. By increasing the flow rate of B2H6/GeH4 from 0.025 to 0.125, more boron related radicals are available to desorb hydrogen atoms from the growing surface. This leads to degradation of the structure of the amorphous phase identified by Raman and X-ray diffraction spectroscopy. The incorporation of boron enhances the carrier concentration from 1.65×1019cm−3 to 2.25×1020cm−3 and reduces the resistivity from 0.131Ω·cm to 0.018Ω·cm as measured by Hall measurement. These highly conductive boron-doped hydrogenated Ge films can be useful as low resistance doped layer in devices to achieve better performance. Moreover, we are able to deposit highly conductive boron-doped Ge films at a low growth temperature (180°C) and low hydrogen dilution ratio (H2/GeH4=33), in this study. Such a low temperature process can overcome some problems with high temperature deposition process that limit application in devices. Furthermore, the low hydrogen dilution ratio can minimize an ion bombardment effect on the films.

Critical investigation on hydrogen bonding by Fourier Transform Infrared spectroscopy in hydrogenated amorphous silicon thin films

Fourier Transform Infrared (FTIR) spectroscopic analysis has been carried out on the hydrogenated amorphous silicon (a-Si:H) thin films deposited by DC, pulsed DC (PDC) and RF sputtering process to get insight regarding the total hydrogen concentration (CH) in the films, configuration of hydrogen bonding, density of the films (decided by the vacancy and void incorporation) and the microstructure factor (R*) which varies with the type of sputtering carried out at the same processing conditions. The hydrogen incorporation is found to be more in RF sputter deposited films as compared to PDC and DC sputter deposited films. All the films were broadly divided into two regions namely vacancy dominated and void dominated regions. At low hydrogen dilutions the films are vacancy dominated and at high hydrogen dilutions they are void dominated. This demarcation is at CH=23at.% H for RF, CH=18at.% H for PDC and CH=14at.% H for DC sputter deposited films. The microstructure structure factor R* is found to be as low as 0.029 for DC sputter deposited films at low CH. For a given CH, DC sputter deposited films have low R* as compared to PDC and RF sputter deposited films. Signature of dihydride incorporation is found to be more in DC sputter deposited films at low CH.

Low-temperature deposition of µc-Si : H thin films by a low-frequency inductively coupled plasma for photovoltaic applications

Low-temperature depositions of Si films from hydrogenated amorphous silicon (a-Si : H) to highly crystallized hydrogenated microcrystalline silicon (µc-Si : H) were realized by the low-frequency inductively coupled plasma (LF-ICP) technique, with low hydrogen dilution (50%) and without any intentional substrate heating. µc-Si : H films with a thin incubation layer (<100 nm), a small grain size (<14 nm), a weak [1 1 1] or [2 2 0] preferred orientation, and a low hydrogen content (4–8%) were obtained (at deposition rates ∼0.4–0.7 nm s−1). The increased crystallinity due to the increasing rf power is accompanied by the improved structural order, lowered impurity contamination and decreased hydrogen content. The compactness of the µc-Si : H film is positively related to crystallinity and independent of the high microstructure factor (>0.8). Low-temperature growth of µc-Si : H is attributed to high atomic H flux and suppression of high-energy ion bombardment due to the high density of low-temperature electrons in the plasma. A µc-Si : H solar cell with a less dense intrinsic layer (on a SnO2 : F glass substrate) exhibits a high Voc (584 mV), showing great potential for photovoltaic applications.

Influence of deposition pressure on p-type a-Si:H window layer doped by trimethylboron for a-Si:H superstrate solar cell in plasma enhanced chemical vapor deposition

Wide bandgap (Eg) p-type window layer is very important for silicon based thin film solar cell to obtain high performance, especially high open-circuit voltage (VOC). In this work, the influence of the deposition pressure on the properties of p-type a-Si:H window layer doped by trimethylboron (TMB) in plasma enhanced chemical vapor deposition (PECVD) was investigated systematically by transmission, Raman, and Fourier transform infrared (FTIR) spectroscopies. As a result, high performance hydrogenated amorphous silicon (a-Si:H) p–i–n superstrate solar cell with VOC up to 927mV was successfully achieved on Asahi Type-U SnO2:F coated glass. In this case, excellent wide bandgap p-type a-Si:H window layer was fabricated under a mild deposition condition, including a low hydrogen dilution ratio (H2/SiH4) of 20, a relatively high deposition temperature of 220°C, which was also adopted for the i-layer and n-layer deposition, and a moderate deposition pressure of about 160Pa. We think it is the compromise between wide Eg and good microstructure quality of the p-layer that brings about the good solar cell performance. Such p-type window layer will be very helpful for the fabrication of a-Si:H solar cell, especially of the cell finished in a single PECVD chamber, due to its mild deposition condition.

Large-Grain Epitaxial Thickening Polycrystalline Silicon Films on AIC-Seed Layer by HWCVD with Different Hydrogen Dilution

A thickening polycrystalline silicon (pc-Si) layer with a grain size of 35 μm was grown on an aluminum-induced crystallization (AIC) Si film, with low and high hydrogen dilution. An AIC seed layer was grown on a glass substrate, and a pc-Si epitaxial layer was deposited on it at 450°C by hot-wire chemical vapor deposition. The AIC seed layer exhibits a highly crystalline structure and enhances the growth of the pc-Si layer. The crystalline fraction (93%) with high hydrogen dilution was larger than that (21%) with low hydrogen dilution, owing to low activation energy for nucleation and grain growth.

Open-circuit voltage analysis of p—i—n type amorphous silicon solar cells deposited at low temperature

This paper identifies the contributions of p—a—SiC:H layers and i—a—Si:H layers to the open circuit voltage of p—i—n type a—Si:H solar cells deposited at a low temperature of 125 °C. We find that poor quality p—a—SiC:H films under regular conditions lead to a restriction of open circuit voltage although the band gap of the i-layer varies widely. A significant improvement in open circuit voltage has been obtained by using high quality p—a—SiC:H films optimized at the “low-power regime" under low silane flow rates and high hydrogen dilution conditions.

The effect of relatively low hydrogen dilution on the properties of carbon-rich hydrogenated amorphous silicon carbide films

Carbon-rich hydrogenated amorphous silicon carbide (a-Si1–xCx:H) films were deposited by plasma enhanced chemical vapor deposition (PECVD) using silane, ethylene and hydrogen as gas sources. The effect of relatively low hydrogen dilution on the properties of as-deposited samples was investigated. A variety of techniques including Scanning Electron Microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Raman scattering (RS), UV-VIS spectrophotometer and photoluminescence (PL) spectroscopy were used to characterize the grown films. The deposition rate decreases with hydrogen dilution. The silicon to carbon ratio increases slightly with the addition of hydrogen. The phenomenon can be attributed to the dissipation of power density caused by hydrogen dilution. Raman G peak position shifting to a lower wave number indicates that hydrogen dilution reduces the size and concentration of sp2 carbon clusters, which is caused by the etching effect by atomic hydrogen. The optical band gap, which is controlled by the sp2 carbon clusters and Si/C ratio, changes unmonotonously. The as-deposited samples exhibited a blue-green room-temperature (RT) PL well visible to the naked eye with UV excitation. The PL band can be attributed to the radiative recombination of electron-hole pairs within small sp2 clusters containing C=C and C-H units in a sp3 amorphous matrix.

From amorphous to microcrystalline: Phase transition in rapid synthesis of hydrogenated silicon thin film in low frequency inductively coupled plasmas

Hydrogenated silicon (Si:H) thin films were fabricated on glass substrates by low frequency inductively coupled plasma-assisted chemical vapor deposition using a silane precursor with low hydrogen dilution at room temperature. The crystallinity and microstructure properties of the Si:H thin films deposited at different inductive radio-frequency (rf) power density were systematically studied by Raman spectroscopy, x-ray diffraction, and scanning electron microscopy. We found that at a low rf power density of 16.7 to 20.8 mW/cm3, the structure of silicon thin films evolves from a completely amorphous phase to an intermediate phase containing both amorphous and microcrystalline silicon. As the power density is increased to a moderate value of 25 mW/cm3, a highly crystallized (111)-preferred hydrogenated microcrystalline silicon (μc-Si:H) film featuring a vertically aligned cone-shaped structure, is emerging. Both the crystallinity and deposition rate exhibit a monotonic increase with the increase in the rf power density, reaching a maximum value of 85% and 1.07 nm/s, respectively, at a power density of 41.7 mW/cm3. Scanning electron microscopy reveals that continuous and dense μc-Si:H films with grain size of tens to hundreds nanometers can be achieved deterministically without the formation of amorphous incubation layer, and this is of great importance for synthesis of multilayer structures in p-i-n solar cells. The formation mechanism of the μc-Si:H films and the elimination of the amorphous incubation layer are explained in terms of the high electron density and the plasma-surface interactions.

Control of preferential orientation of microcrystalline silicon and its impact on solar cell performance

AbstractThe significance of preferential orientation in microcrystalline silicon for its post‐oxidation properties and solar cell performance has been investigated in the high crystalline volume fraction range. The degree of &lt;110&gt; preferential orientation can be varied by changing hydrogen/silane ratio in plasma enhanced chemical vapor deposition, and the crystalline volume fraction is lowered for a &lt;110&gt; oriented sample at the low hydrogen dilution ratio. In this study, we have improved the volume fraction by a seeding method, and, even under low hydrogen dilution, we have successfully controlled the preferential orientation of the samples with equivalently high crystalline‐volume‐fraction. Films in strong &lt;110&gt;‐preferential‐orientation show little amount of post‐oxidation, and the sharp signal at around 2100 cm−1 in the infrared (IR) absorption spectrum appears as the preferential orientation turns from the &lt;110&gt; to the &lt;111&gt; direction. The solar cell performance well agrees with the post‐oxidation properties. The origin of these preferential orientation impacts on post‐oxidation and on solar cell performance is discussed in terms of amorphous silicon passivation on the grain boundaries (GBs) presumably influenced by hydrogen/silane ratio. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Fabrication of thin film silicon solar cells on plastic substrate by very high frequency PECVD

The paper describes the way to transfer process technology of state-of-the-art high efficiency thin film silicon solar cells fabrication on cheap plastic (such as PET or PEN) substrates, by two completely different approaches: (i) by transfer process (Helianthos concept) of thin film silicon cells deposited at high substrate temperature, T s (∼200 °C) and (ii) direct deposition on temperature sensitive substrates at low T s (∼100 °C). Adaptation of the process parameters and cell processing to the requirement of the flexible/plastic substrate is the most crucial step. In-situ diagnosis of the plasma has been done to understand the effect of inter-electrode distance, substrate temperature and hydrogen dilution on the gas phase conditions. Whereas, for the transfer process, the inter-electrode distance is a critical deposition condition that needs to be adapted for the flexible substrates, the direct deposition on plastic substrates has an added issue of loss in material quality and the deposition rate due to depositions at low T s. Our studies indicate that ion energy is crucial for obtaining compact films at low temperature and high hydrogen dilution helps to compensate the loss of ion energy at low substrate temperatures. Efficiencies of ∼5.9% and 6.2% have been obtained for n–i–p type a-Si cells on PET and PEN substrates, respectively, using direct deposition. Using an adapted inter-electrode distance, an a-Si/nc-Si tandem cell on plastic (polyester) substrate with an efficiency of 8.1% has been made by Helianthos cell transfer process.

Si quantum dots embedded in an amorphous SiC matrix: nanophase control by non-equilibrium plasma hydrogenation

Nanophase nc-Si/a-SiC films that contain Si quantum dots (QDs) embedded in an amorphous SiC matrix were deposited on single-crystal silicon substrates using inductively coupled plasma-assisted chemical vapor deposition from the reactive silane and methane precursor gases diluted with hydrogen at a substrate temperature of 200 degrees C. The effect of the hydrogen dilution ratio X (X is defined as the flow rate ratio of hydrogen-to-silane plus methane gases), ranging from 0 to 10.0, on the morphological, structural, and compositional properties of the deposited films, is extensively and systematically studied by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier-transform infrared absorption spectroscopy, and X-ray photoelectron spectroscopy. Effective nanophase segregation at a low hydrogen dilution ratio of 4.0 leads to the formation of highly uniform Si QDs embedded in the amorphous SiC matrix. It is also shown that with the increase of X, the crystallinity degree and the crystallite size increase while the carbon content and the growth rate decrease. The obtained experimental results are explained in terms of the effect of hydrogen dilution on the nucleation and growth processes of the Si QDs in the high-density plasmas. These results are highly relevant to the development of next-generation photovoltaic solar cells, light-emitting diodes, thin-film transistors, and other applications.

Rapid, low-temperature synthesis of nc-Si in high-density, non-equilibrium plasmas: enabling nanocrystallinity at very low hydrogen dilution

Nanocrystalline silicon thin films were deposited on single-crystal silicon and glass substrates simultaneously by inductively coupled plasma-assisted chemical vapor deposition from the reactive silane reactant gas diluted with hydrogen at a substrate temperature of 200 °C. The effect of hydrogen dilution ratio X (X is defined as the flow rate ratio of hydrogen to silane gas), ranging from 1 to 20, on the structural and optical properties of the deposited films, is extensively investigated by Raman spectroscopy, X-ray diffraction, Fourier transform infrared absorption spectroscopy, UV/VIS spectroscopy, and scanning electron microscopy. Our experimental results reveal that, with the increase of the hydrogen dilution ratio X, the deposition rate Rd and hydrogen content CH are reduced while the crystalline fraction Fc, mean grain size δ and optical bandgap ETauc are increased. In comparison with other plasma enhanced chemical vapor deposition methods of nanocrystalline silicon films where a very high hydrogen dilution ratio X is routinely required (e.g. X > 16), we have achieved nanocrystalline silicon films at a very low hydrogen dilution ratio of 1, featuring a high deposition rate of 1.57 nm/s, a high crystalline fraction of 67.1%, a very low hydrogen content of 4.4 at.%, an optical bandgap of 1.89 eV, and an almost vertically aligned columnar structure with a mean grain size of approximately 19 nm. We have also shown that a sufficient amount of atomic hydrogen on the growth surface essential for the formation of nanocrystalline silicon is obtained through highly-effective dissociation of silane and hydrogen molecules in the high-density inductively coupled plasmas.

Structural order of thin film silicon made at 100 °C

AbstractSpectroscopic ellipsometric measurements showed that amorphous silicon thin films made by very high frequency plasma enhanced chemical vapour deposition at 100 °C using an optimum H2 dilution has denseness (A parameter) and structural order (C parameter) that are comparable to the sample made at 200 °C. The materials made by hot wire chemical vapour deposition (HWCVD) at low hydrogen dilution conditions have a less dense structure and higher roughness compared to the plasma deposited samples. The C parameter reaches the lowest value (C=1.67) for the HWCVD sample made at an optimum H2/SiH4 ratio of 20, even though it was made only at 100 °C. The importance of filament to substrate distance in HWCVD process in suppressing the undesirable species reaching at the growing surface has been put forward to achieve materials with very small structural disorder and fabrication of thin film silicon solar cells with high stability. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Influence of Hydrogen Dilution of Silane on the Properties of nc-Si:H Films Grown by Layer-by-Layer Deposition Technique

Hydrogenated nanocrystalline silicon (nc-Si:H) films produced by layer-by-layer (LBL) deposition technique were studied. The films were grown at different hydrogen to silane flow-rate ratio on crystal silicon (111) substrate. The properties of films were investigated by X-ray diffraction (XRD), micro-Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, optical transmission spectroscopy, atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). These properties showed dependence on the hydrogen dilution of silane. Appearance of XRD peaks at diffraction angles of 28.4 o and 56.1 o which correspond to silicon orientation of (111) and (311) respectively, were observed in all films indicating evidence of crystallinity in the films. Raman scattering results indicated that crystallinity in the films was due to the presence of nanocrystallites embedded in an amorphous matrix. The energy gap of the films showed dependence on the hydrogen content in the films. Increase in nanocrystallite size resulted in increase in disorder at low hydrogen dilution films but films remain homogenous with increase in nanocrystallite size for the high hydrogen dilution films.