Search

A study was conducted to investigate the origins of the very low hydrogen concentrations observed in the a-Si:H films prepared by using a triode deposition system. The finding reveal that due to a steric hindrance, the hydrogen elimination process during film growth is disturbed when higher silane radicals stick to a growth surface which contributes to short diffusion length and frequent collisions with silane molecules.

Very thin microcrystalline silicon films were deposited by plasma-enhanced chemical vapor deposition from hydrogen diluted SiH4 gas to examine its initial growth process. The dependence of the crystallinity and the Si-H bonding configuration on electrical and chemical characteristics of substrates were investigated utilizing a high sensitivity Raman spectrometer. Findings revealed that conductive and oxygen free substrates offer good crystallinity in the initial stage.

A highly stabilized hydrogenated amorphous silicon film was developed using a triode deposition system in which a mesh was installed between cathode and substrate in a plasma-enhanced chemical vapor deposition system. The hydrogen concentrations of the resulting films are very low compared with those of conventional films prepared at the same substrate temperature. It was observed that light-soaking stability of the obtained film is promising, which is confirmed by measuring a neutral spin density as well as an I-V characteristic of a Schottky diode. Reduction of densities of higher silane radicals during film growth is an important factor for controlling degradation. [ABSTRACT FROM AUTHOR]

By applying real-time spectroscopic ellipsometry and infrared attenuated total reflection spectroscopy (ATR), we have characterized interface-layer formation in microcrystalline silicon (µc-Si:H) growth on ZnO substrates in a conventional rf plasma-enhanced chemical vapor deposition. With an increase in the hydrogen dilution ratio (R=[H[sub 2]]/[SiH[sub 4]]), we find a significant increase in the interface-layer thickness from 0 (R=0) to 48 Å(R=100). In contrast, no interface-layer formation was observed in µc-Si:H growth on SiO[sub 2] substrates. Detailed analyses show that the interface layer formed on ZnO is porous amorphous Si:H with a large amount of SiH[sub 2] bonds (16 at. %). During the early stage of interface-layer formation, we observed almost no film deposition and a dramatic increase in free-carrier concentration within the ZnO substrate due to a chemical reduction of ZnO by H-containing plasma. Real-time ATR spectra revealed the predominant formation of SiH[sub n] O[sub 4-n] (n = 1-2) species on the ZnO surface prior to interface-layer formation. These SiH[sub n]O[sub 4-n] species are chemically inactive and remain at the µc-Si:H/ZnO interface. Based on these findings, we propose that the SiH[sub n]O[sub 4-n] formation that results from ZnO reduction reaction by H suppresses chemical reactivity on the ZnO surface and induces porous interface-layer formation during the initial deposition process. [ABSTRACT FROM AUTHOR]

Real-time infrared attenuated total reflection (ATR) spectroscopy and spectroscopic ellipsometry (SE) have been applied to assess depth profiles of Si-H[sub n] (n = 1 - 2) bonding modes in Si:H thin films. We have established an ATR data analysis procedure and the depth profiles of the Si-H[sub n] bonding modes were readily obtained from incorporation rates of Si-H[sub n] bonds at each film thickness estimated by SE. In an attempt to investigate the nucleation reaction of microcrystalline silicon (μc-Si:H) from the hydrogenated amorphous silicon (a-Si:H) phase, a series of Si:H thin films were prepared by an rf plasma-enhanced chemical vapor deposition using various hydrogen dilution ratios R = [H[sub 2]]/[SiH[sub 4]]. Real-time ATR and SE revealed that hydrogen content in the a-Si:H layers is uniform toward the growth direction. On the contrary, in the μc-Si:H film deposited at high R, a drastic reduction in the Sill hydrogen content is observed after the μc-Si:H nucleation, whereas the SiH[sub 2] hydrogen content is not sensitive to the phase transition. We find a weak variation in the hydrogen content in the a-Si:H layers deposited at various R, and no significant changes are observed in the a-Si:H bulk layers formed at onsets of μc-Si:H nucleation. The above results suggest that the μc-Si:H nucleation reaction occurs near the a-Si:H surface, but not in the a-Si:H bulk layer. [ABSTRACT FROM AUTHOR]

Focuses on a study that investigated spectroscopic diagnostics of plasma-chemical-vapor deposition from silane and germane. Details of the experiment; Results and discussion; Conclusion.

Presents a study which investigated the deposition kinetics of hydrogenated amorphous silicon (a-Si:H) from a SiH[sub4] glow-discharge plasma, by examining the diffusion of SiH[sub3] monoradicals in the discharge-free space within a triode reactor. Processes which classified the deposition of a-Si:H; Schematic of the experimental setup; Dependence of the deposition rate on T[subs] in the diffusion regime; Discussion on thermal H-elimination reaction.

Investigates the dark current-voltage (J-V) characteristics of p-i-n hydrogenated amorphous silicon diodes with various thicknesses of the intrinsic layer. Data on the thickness dependence of J-V characteristics of p-i-n diodes at room temperature; Structures of the diodes.

Presents a study which determined the rotational temperature of silane molecules in a flowing gas as well as in a radio-frequency discharge plasma of silane. Experiment; Results; Discussion.

Examines the silicon nuclear magnetic resonance (NMR) spectra for amorphous hydrogenated silicon (α-Si:H) and amorphous-microcrystalline mixed-phase hydrogenated Si. Information on α-Si:H and amorphous-microcrystalline mixed-phase hydrogenated Si; Relationship between the SI NMR spectra for α-Si:H and amorphous-microcrystalline mixed-phase hydrogenated Si; Analysis of the spatial distribution of hydrogen in α-Si:H.