Effects of Growth Parameters on Surface-morphological, Structural and Electrical Properties of Mo Films by RF Magnetron
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1123-P05-18
Effects of Growth Parameters on Surface-morphological, Structural and Electrical Properties of Mo Films by RF Magnetron Sputtering Shou-Yi Kuo1,2, Liann-Be Chang1,2, Ming-Jer Jeng1,2, Wei-Ting Lin1,2 Yong-Tian Lu3 and Sung-Cheng Hu3 1 Department of Electronic Engineering, Chang Gung University, 2 Green Technology Research Center, Chang Gung University, 259 Wen-Hwa 1st Road, Kweishan, Taoyuan 333, Taiwan 3 Chemical Systems Research Division, Chung-Sung institute of Science & Technology ABSTRACT This work reports on the fabrication and characterization of Mo thin films on soda-lime glass substrate grown by reactive RF magnetron sputtering. Film thickness was measured by αstep surface profiler. The structural properties and surface morphology were analyzed by x-ray diffraction (XRD), atomic force microscope (AFM) and scanning electron microscopy (SEM). Electrical properties were measured by four-point probe. It was found that the growth parameters, such as argon flow rate, RF power, film thickness, have significant influences on properties of Mo films. The strain on films revealed the complicated relationship with the working pressure, which might be associated with micro structures and impurities. In order to improve the adhesion and electricity, we adopted a two-pressure deposition scheme. The optimal thickness and sheet resistance are 1 μm and 0.12 Ω/□. The mechanisms therein will be discussed in detail. Furthermore, we also investigated the diffusion property of Na ion of double Mo films sputtered on soda-lime glass. Our experimental results could lead to better understanding for improving further CIGS-based photovoltaic devices. INTRODUCTION Molybdenum (Mo) is commonly used as back contacts for Cu(In,Ga)Se2 (CIGS) thin film solar cells because it has good electrical properties and is an inert, mechanically durable substrate during the absorber film growth [1]. A wide variety of other materials such as W, Ta, Nb, Cr, V, Ti, and Mn have also been investigated without any improvement compared to Mo, and often lower cell efficiency due to chemical reactivity. CIGS thin film growth occurs at the temperatures above 500 0C and the thermally induced extrinsic stresses in the glass-Mo structure may cause bending or mechanical distortion of substrate. During the formation of CIGS films, Na ions might diffuse from the soda-lime glass substrate through the Mo back contact into the absorber layer. The diffusion of Na into the absorber film depends on the deposition conditions of the Mo back contact. Thus, to fabricate high-efficiency CIGS solar cells, we need to understand the properties of sputtered Mo films. The deposition parameters and process play a key role in obtaining a layer with the appropriate properties. Extensive research has been done on the deposition of Mo thin films by dc sputtering. In this article, we report the surface morphology, structural, electrical and strain properties of Mo thin films prepared by RF magnetron sputtering.
EXPERIMENT Molybdenum (Mo) thin films were deposited on soda-lime
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