Madhusudan Jana

Characterization of undoped μc-SiO:H films prepared from (SiH4+CO2+H2)-plasma in RF glow discharge

Undoped hydrogenated microcrystalline silicon oxygen alloy films (μc-SiO:H) have been prepared from (SiH4+CO2+H2)-plasma in RF glow discharge at a high H2 dilution, moderately high RF power and substrate temperature. A detailed characterization of the films has been done by electrical, optical as well as structural studies, e.g., IR absorption spectroscopy, Raman scattering and transmission electron microscopy. The presence of a very small amount of oxygen induces the crystallization process, which fails to sustain at a higher oxygen dilution. At higher deposition temperature and in improved μc-network H content reduces, however, O incorporation is favoured. Sharp crystallographic rings in the electron diffraction pattern identify several definite planes of c-Si and no such crystal planes from c-SiOX is detected.

Heterogeneity in microcrystalline-transition state: Origin of Si-nucleation and microcrystallization at higher rf power from Ar-diluted SiH4 plasma

Using very high Ar-dilution to the SiH4 plasma, good quality amorphous Si:H films could be obtained at very low rf power. The a-Si:H film, prepared at a very low deposition rate of ∼10 A/min, exhibited a σPh∼1×10−4 S cm−1, σPh/σD∼105, a notably wide optical gap of 2.10 eV and a very good stability against thermal annealing effects with reasonable light induced degradation. At higher rf power undoped μc-Si:H films were prepared with a high σD∼1×10−4 S cm−1, at a deposition rate of 30 A/min from <1 sccm of SiH4. Micrograins were identified with several well-defined crystallographic orientations. However, porosity in the grain boundary zone contributed a significant amount of adsorbed effects on the electrical properties. At very high powers, the growth of a columnar network structure was demonstrated. Long-range structural relaxation permitted by the non-rigid and heterogeneous network structure associated with the physical vapor deposition-like growth at the microcrystalline-transition state, has been iden...

Role of hydrogen in controlling the growth of μc-Si:H films from argon diluted SiH4 plasma

Hydrogenated microcrystalline silicon thin films have been prepared by the rf glow discharge method using argon as a diluent of SiH4 to achieve a high growth rate. μc-Si:H film having conductivity ∼10−5 S cm−1 was achieved at a deposition rate of 36 A/min at a moderate power density of 90 mW/cm2, without hydrogen dilution. Micrograins were identified with several well defined crystallographic orientations. Inhomogeneity and porosity at the grain boundary zone have a significant effect on the electrical properties of the films due to adsorption when exposed to atmosphere. However, by adding hydrogen to the Ar-diluted SiH4 plasma, a homogeneous and improved network structure without having any effect of adsorption was obtained at a reduced deposition rate. Highly conducting (σD∼10−3 S cm−1) undoped μc-Si:H film was prepared at a deposition rate of 15 A/min having 90% crystalline volume fraction. The energy released by the de-excitation of Ar* in the plasma initiates rapid nucleation in the Si network and at...

Control of Crystallization at Low Thickness in µc-Si:H Films Using Layer-by-Layer Growth Scheme

Hydrogen plasma treatment of stacking layers in a layer-by-layer (LBL) growth scheme effectively modulates the network structure from the surface into the bulk through the growth zone by abstraction of hydrogen from the Si:H matrix. It is an efficient way of reducing the microcrystalline transition layer so that virtual saturation of the crystallization may be obtained at a significantly low thickness of the sample compared to that obtained by a continuous mode of deposition. The growth of a highly conducting undoped µc-Si:H film at a stacked layer thickness of ~650 A is described. The film has a dark conductivity, σD, of ~4×10-3 Scm-1 and exhibits a very high crystallinity, as determined by Raman scattering and transmission electron microscope studies.

Correlation of electrical, thermal and structural properties of microcrystalline silicon thin films

Thermal diffusivity (α) has been correlated with the electrical and structural properties of hydrogenated microcrystalline silicon (µc-Si:H) films. In the heterogeneous microcrystalline network, α and electrical conductivity (σD) maintain a one-to-one correspondence, and both these parameters are directly related to the crystalline volume fraction (Fc) of the network. For the amorphous silicon network, α is ~ 0.2 cm2s1 and has a very low σD of ~ 10-8 Scm-1. When the crystalline volume fraction (Fc) exceeds a certain percolation threshold, both α and σD increase abruptly. Undoped µc-Si:H films having Fc~94% exhibit a high magnitude of α~0.80 cm2s-1 and a very high σD of ~ 10-3 Scm-1.

Fast deposition of /spl mu/c-Si:H films from Ar-diluted SiH/sub 4/ plasma in RF glow discharge

Using Ar as diluent for SiH/sub 4/ in RF glow discharge, we obtained undoped and doped /spl mu/c-Si:H films having high /spl sigma//sub D/ low /spl Delta/E and low /spl alpha/; exhibiting sharp crystallographic rings in the electron diffraction pattern, c-Si grains of 100 /spl Aring/ diameter in the micrograph and intense Raman peak around 520 cm/sup -1/. The films were prepared at a remarkably high deposition rate of 50-70 /spl Aring//min contributed from SiH/sub 4/ having a flow rate of 1 SCCM, and hence it provides enormous promise towards an economic throughput in the fabrication of devices using this material.