Himanshu S. Jha

Nanocrystalline cubic Silicon Carbide thin films for the window layer of solar cells deposited by Hot Wire CVD

Nanocrystalline cubic silicon carbide (nc-3C-SiC) films are deposited using hot wire chemical vapour deposition technique at ~350 °C on glass substrates using SiH4 /CH4/H2 as precursor gases. We investigated the influence of total gas pressure on the structural, optical and transport properties of nc-3C-SiC films. Raman scattering spectra and X-ray diffraction patterns revealed that the film prepared below 2 mbar is nanocrustalline silicon (nc-Si), while at ≥ 2 mbar films are nc-3C-SiC. We achieved high deposition rate (≥ 14-20 nm/min), high optical band gap (3.2-3.4 eV) and high conductivity (~ 10-4 -10-2 Ω-1cm-1) suitable for window layer for Solar cells.

Study of the growth of graphene film on Ni and Si substrates by hot filament chemical vapor deposition

Graphene films were prepared on Ni and heavily doped Si substrates simultaneously by hot filament chemical vapor deposition. Films were prepared at two sets of parameters: at 3 mbar process pressure, 600 °C substrate temperature and also at 2 mbar process pressure, 800 °C substrate temperature. Field emission scanning electron microscopy images show vertical growth of graphene films on Si substrates and planer growth on Ni substrates. Raman spectroscopy was used to study the phonon modes on the prepared films. The observed intensity ratio of ID/IG ∼0.1 and IG/I2D ∼2.5 in films grown on Ni substrate indicates the formation of more than 10-15 layers of defect free graphene films.

Synthesis of high density nucleation of nano-crystalline diamond films on non carbon affinity substrates

Thin films of nano-crystalline diamond (NCD) were grown on c-Si (100) substrates using a gas mixture of methane (CH4) and hydrogen (H2) by hot filament chemical vapor deposition technique. No special pretreatment of substrate for enhancement of nucleation center was employed. Films were prepared at low substrate temperature of 430-450 °C and a low chamber pressure of 2 mbar with varying CH4 gas concentration. The concentration of CH4 gas in the mixture of CH4 and H2 was varied from ∼10-70%. The growth rate for the diamond particles achieved was of the order of ∼ 10 nm/min. Films were characterized using x-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM), which confirmed the growth of NCD. The grown films have both type of carbon bonding sp3 as well as sp2. The average particle size estimated by FESEM image was in the range of 50-200 nm. The nucleation density of the diamond particles as obtained from FESEM image was approximately 108-1010/cm2, and it was fo...

Fabrication of two dimensional carbon nanostructures using hotwire chemical vapor deposition technique

Two dimensional carbon nanostructures (carbon nanosheets) are fabricated using Hot Wire Chemical Vapor Deposition (HWCVD) technique assisted by H radical injection, using CH4 as source gas. Carbon nanosheets are grown on crystalline Si(100) wafer as well as on corning glass substrate without using catalyst. The grown carbon nanosheets are aligned vertically on the substrate with thickness in the range of 10-20 nm and about 60-80 nm in height.

DoS Using SCLC Measurements in Hydrogenated Silicon Films

Density of defect states (DoS) play a significant role in controlling the optoelectronic properties and performance of semiconductor devices. Space charge limited current measurements is a simple method to estimate the approximate density of states near Fermi level in semiconducting thin films.