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1153-A18-03

First-principles modeling of structure, vibrations, electronic properties and bond dynamics in hydrogenated amorphous silicon: theory versus experiment A.I. Shkrebtii1,*, I.M. Kupchak1,2, and F. Gaspari1 1 2

University of Ontario Institute of Technology, Oshawa, ON, L1H 7L7, Canada V. Lashkarev Institute of Semiconductor Physics NAS, Kiev, 03028, Ukraine

ABSTRACT We carried out extensive first-principles modeling of microscopic structural, vibrational, electronic properties and chemical bonding in hydrogenated amorphous silicon (a-Si:H) in a wide range of hydrogen concentration and preparation conditions. The theory has been compared with experimental results to comprehensively characterize this semiconductor material. The computer modeling includes ab-initio Molecular Dynamics (MD), atomic structure optimization, advanced signal processing and computer visualization of dynamics. We extracted parameters of hydrogen and silicon bonding, electron charge density and calculated electron density of states (EDOS) and hydrogen diffusion. A good agreement of the theory with various experiments allowed us to correlate microscopic processes at the atomic level with macroscopic properties. Here we focus on correlation of the amorphous structure of the material, atom dynamics and electronic properties. These results are of increasing interest due to extensive application of aSi:H in modern research and technology and to the significance of detailed understanding of the material structure, bonding, disordering mechanisms and stability. INTRODUCTION The utilization of sophisticated computer modelling to analyze structure and dynamical processes in solid state, including amorphous materials, allows the uncovering of many of their characteristics which are difficult or even impossible to isolate and analyze experimentally1,2. Hydrogenated amorphous silicon (a-Si:H) has been the subject of intensive investigation for over 30 years; there exists extensive literature covering all of its most important properties and applications3,4. The main role of hydrogen in amorphous silicon is to passivate the Si dangling bonds (DBs) to restore a proper energy gap and semiconducting properties, thus enabling application of a-Si:H in microelectronics and photovoltaics. Due to the importance of hydrogen, many experimental methods have been used to characterize DB passivation, H-Si bonding and related mechanisms of degradation. Among the numerous experimental techniques to investigate a-Si:H and the role of hydrogen, Fourier Transform Infrared Spectroscopy (FTIR) is used extensively to analyze vibrational spectra of a-Si:H. Although FTIR represents one of the most common and powerful characterization techniques, no microscopic links between the observed vibrational spectra and the microscopic properties of a-Si:H have been established. Other important experimental techniques such as Isothermal Capacitance Transient Spectroscopy (ICTS) and Constant Photocurrent method (CPM) are widely used for the determination of EDOS, (for a review o