C. M. S. Rauthan

Investigation of radio frequency plasma for the growth of diamond like carbon films

The radio frequency has been used to generate plasma of argon, acetylene gases, and their mixture should be replaced by mixture in a plasma enhanced chemical vapor deposition system. The generated plasma discharge has been characterized by an impedance analyzer (VI probe) for the evaluation of various electrical parameters of the plasma discharge such as rf-voltage, rf-current, phase, impedance, and actual power consumed by the plasma discharge. These plasma parameters have been analyzed as a function of self-bias, which are found to depend on applied power, pressure, and reactor geometry of the system. Subsequently, same plasma conditions were used for the deposition of diamond like carbon (DLC) films. The argon plasma has lowest impedance (16.02 Ω) value and highest average electron density (2.77u2009×u20091010u2009cm−3) value at −150 V self-bias. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy measurements have been performed on the prepared DLC films for the evaluation of the chemical bonding. XPS s...

Effect of Hydrogen Content and Bonding Environment on Mechanical Properties of Hydrogenated Silicon Films Deposited by High-Frequency PECVD Process

The mechanical properties of hydrogenated silicon thin films deposited using high-frequency PECVD process were studied, which certainly have importance for optoelectronic devices particularly for getting stability and long operating lifetime in harsh conditions. Nanoindentation technique was used to measure the load versus displacement curves, hardness (H), elastic modulus (E), plastic resistance parameter (H/E), elastic recovery (ER), and plastic deformation energy (𝑈𝑟), while laser scanning stress measurement setup was used to measure the intrinsic stress of these films. The concentration of bonded hydrogen in these films was found in the range of 3.6 to 6.5 at. % which was estimated using integrated intensity of IR absorption peak near 640 cm−1. Dependence of mechanical properties of these films on hydrogen content and bonding environment has been investigated. The film containing minimum hydrogen content (3.6%) shows the maximum elastic recovery (52.76%) and minimum plastic deformation energy (3.95×10−10 J). Surface roughness measured by AFM was found to decrease with the increase in hydrogen content in the film. The dependency of stress on the plasma frequency and applied power has also been discussed.

Role of Sandwich Cu Layer in and Effect of Self-Bias on Nanomechanical Properties of Copper/Diamond-Like Carbon Bilayer Films

The role of sandwich Cu layer in and effect of self-bias on structural and nanomechanical properties of Cu/DLC bilayer films have been explored. Cu/DLC bilayer films were grown, under varied self-bias from −125 to −225 V, using hybrid system involving radio-frequency- (RF-) plasma-enhanced chemical vapor deposition and RF-sputtering units. Surface topography and mean roughness was studied by atomic force microscope and then correlated with mechanical properties. The addition of sandwich Cu layer in DLC reduces its residual stress and does not affect bilayer film hardness and elastic modulus. Load versus displacement was also employed to estimate various other mechanical parameters, which further correlated with self-bias and structural properties. These Cu/DLC bilayer films seem to be a potential candidate for various industrial applications such as hard and protective coating on cutting tools, solar cells, and wear resistance coating on magnetic storage media.

Band gap engineering of hydrogenated amorphous carbon thin films for solar cell application

In this work, self bias variation, nitrogen introduction and oxygen plasma (OP) treatment approaches have been used for tailoring the band gap of hydrogenated amorphous carbon (a-C:H) thin films. The band gap of a-C:H and modified a- C:H films is varied in the range from 1.25 eV to 3.45 eV, which is found to be nearly equal to the full solar spectrum (1 eV- 3.5 eV). Hence, such a-C:H and modified a-C:H films are found to be potential candidate for the development of full spectrum solar cells. Besides this, computer aided simulation with considering variable band gap a-C:H and modified a- C:H films as window layer for amorphous silicon p-i-n solar cells is also performed by AFORS-HET software and maximum efficiency as ~14 % is realized. Since a-C:H is hard material, hence a-C:H and modified a-C:H films as window layer may avoid the use of additional hard and protective coating particularly in n-i-p configuration.

Growth of nanocrystalline silicon films by VHF PECVD

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited using very high frequency (VHF) plasma enhanced chemical vapor deposition (PECVD) technique at 60 MHz. Films were grown at different power from 5 W to 40 W. The maximum deposition rate was found to be 6.1 A0/sec at 20 W power. These films were characterized by XRD which revealed that the size of the Si nanocrystals are in the range of 15.7 to 19.6 A0. The optical band gap was found in the range between 1.64 to 1.74 eV.

Simulation studies on heterojunction and HIT solar cells

Heterojunction solar cells have shown a promising comparable efficiency with the advantage of lower fabrication cost compared to the crystalline solar cells. In this paper, an attempt has been made to simulate the heterojunction structure and HIT structure using AMPS-1D software by applying various approaches. The simulation parameters of these structures are varied for cell efficiency, quantum efficiency, charge carrier concentration and temperature stability to achieve higher efficiency. The final solar cell parameters have been achieved about 20% for heterojunction and 23% for HIT cells. The effects on intrinsic and extrinsic characteristics of doped layers are discussed for these efficiencies.