arXiv subjects

Neha Sharma

Publications and source records attributed to Neha Sharma.

22 records · Page 2Linked to original sources

arXiv2016

Optical band gap and associated band-tails in nanocrystalline AlN thin films grown by reactive IBSD at different substrate temperatures

AlN thin films have been grown on Si (100) substrates by reactive ion beam sputter deposition (IBSD) at different substrate temperatures varying from room temperature (RT) to 500oC. Substrate temperature induced microstructural transition from amorphous at RT, nanocrystalline at 300oC to microcrystalline at 400oC has been observed by Transmission Electron Microscopy (TEM). Average surface roughness (Ra) and morphology has been explored by using Atomic Force Microscopy (AFM). UV-VIS spectrophotometry has been employed to probe the substrate temperature induced changes in optical band-gap (Eg) of grown thin films in reflectance mode. It was found that Eg was increased from 5.08 to 5.21 eV as substrate temperature was increased from RT to 500oC. Urbach energy tail (Eu) along with weak absorption tail (WAT) energy (Et) have been estimated to account for the optical disorder which was found to decrease with associated increase in Eg.

cond-mat.mtrl-sci↗

arXiv2015

XPS studies on AlN thin films grown by ion beam sputtering in reactive assistance of N+/N2+ ions: Substrate temperature induced compositional variations

We report on an XPS study of AlN thin films grown on Si(100) substrates by ion beam sputter deposition (IBSD) in reactive assistance of N+/N2+ ions to unravel the compositional variation of their surface when deposited at different substrate temperatures. The temperature of the substrate was varied as room temperature (RT), 100oC and 500oC. The binding energy of Al-2p, N-1s and O-1s core electrons indicate the formation of 2H polytypoid of AlN. The increase in concentration of AlN with substrate temperature during deposition is elucidated through detailed analysis with calculated elemental atomic concentrations (at. %) of all possible phases at the film surface. Our results show that predominate formation of AlN as high as 74 at. % is achievable using substrate temperature as the only process parameter. This high fraction of AlN in thin film surface composition is remarkable when compared to other growth techniques. Also, the formation of other phases is established based on their elemental concentrations.

cond-mat.mtrl-sci↗

arXiv2014

Growth Kinetics of Ion Beam Sputtered Al-thin films by Dynamic Scaling Theory

This paper reports the study of growth kinetics of ion beam sputtered aluminum thin films. Dynamic scaling theory was used to derive the kinetics from AFM measurements. AFM imaging revealed that surface incorporates distinctly different morphologies. Variation in deposition times resulted in such distinctiveness. The growth governing static (alpha) as well as dynamic (beta) scaling exponents have been determined. The exponent (alpha) decreased as the deposition time increased from 3 to 15 minutes. Consequently, the interfacial width (xi) also decreased with critical length (Lc), accompanied with an increase in surface roughness. Surface diffusion becomes a major surface roughening phenomenon that occurs during deposition carried out over a short period of 3 minutes. Extension of deposition time to 15 minutes brought in bulk diffusion process to dominate which eventually led to smoothening of a continuous film.

cond-mat.mtrl-sci↗

arXiv2014

Growth Kinetic studies of ion beam sputtered AlN-thin films: Effect of reactive assistance of nitrogen plasma

Reactive dual ion beam sputter deposition of AlN thin films was carried out for the analysis of surface growth characteristics by Atomic Force Microscopy. The variation of roughness as a function of deposition time was analysed by Dynamic Scaling Theory (DST). Two distinct exponents, static and dynamic were used to unravel the film growth characteristics. As the deposition time increased, static scaling exponent decreased gradually and substrate surface coverage was increased which is indicated by a decrease in critical length Lc. The rms roughness of the film was increased from 1.99 to 3.42 nm as the deposition time was increased from 3 minutes to 15 minutes. Dynamic scaling exponent was found to be 0.36. During the growth, surface diffusion (n = 4) becomes the major roughening phenomenon while Bulk diffusion (n = 3) turns into the dominating smoothening phenomenon.

cond-mat.mtrl-sci↗