Pulsed Laser Deposition Parameter Optimization for Growth of Alumina (Al 2 O 3 ) Thin Film on Silicon (100)
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Pulsed Laser Deposition Parameter Optimization for Growth of Alumina (Al2O3) Thin Film on Silicon (100) Xinyu Wang, Sergey Yarmolenko, Dhananjay Kumar, Zhigang Xu, Jagannathan Sankar Department of Mechanical and Chemical Engineering, Center for Advanced Materials and Smart Structures, North Carolina A&T State University, 1601 E. Market Street, Fort IRC Building, Room 242, Greensboro, NC 27411, USA ABSTRACT Pulsed laser deposition (PLD) technique was used to grow alumina (Al2O3) thin films on (100) silicon substrate under different deposition conditions. The relationship between Al2O3 thin film thickness, hardness, elastic modulus, surface morphology and PLD parameters such as laser energy and substrate temperature was investigated. The Film thickness was found to increase with an increase in laser energy and to decrease with an increase in substrate temperature. The film hardness and elastic modulus increases as substrate temperature increases. We have also shown that films are amorphous at lower substrate temperatures and transform to mixture of amorphous and crystalline phases. The ratio of amorphous to crystalline phases decreases with increase in temperature. The surfaces of Al2O3 film grown using PLD was found very smooth with least root square roughness less than 2 nm. INTRODUCTION Alumina (Al2O3) is one of the most popular engineering ceramics offering excellent electrical insulation properties together with high hardness and good wear resistance. It can be deposited on the surface on some soft materials as thin film to form a hard and strong surface. In a pulsed laser deposition (PLD) technique, a pulsed laser beam strikes the surface of the solid target and evaporates the target materials which subsequently deposit on the substrate. PLD has the ability to replicate the composition of the target onto the film very accurately. For this and other benefits, PLD technique is becoming one of the most popular means of obtaining excellent quality films of various materials. There are several PLD parameters that influence the deposition process: laser energy (or intensity), laser wavelength, number of laser pulses, laser frequency, distance between substrate and target, substrate temperature, ambient gas pressure, laser output aperture size. Several studies have been done to find the influence of these PLD parameters on the deposited film properties [1-4]. However, all these studies were done for different materials and systematic study for a specific material such as Al2O3 is surprisingly limited. The purpose of this study was to establish a relationship between PLD parameters and Al2O3 thin film properties and optimize PLD parameters. Our present study was focused on finding the effect of the two most predominant PLD parameters, namely laser energy and substrate temperature on the Al2O3 film properties. The Al2O3 film properties that we have investigated are thickness, hardness and elastic modulus.
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EXPERIMENTAL DETAILS Experiments were conducted in a stainless-steel chamber evacuated by a turbo
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