Seed-Free Growth of Diamond Patterns on Femtosecond Laser Processed Silicon Substrates
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Seed-Free Growth of Diamond Patterns on Femtosecond Laser Processed Silicon Substrates Mengmeng Wang,1,2 Yunshen Zhou,1 Z. Q. Xie,1 Y. Gao,1 Lan Jiang,2 Yongfeng Lu1 1 Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0511, U.S.A. 2 School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China. ABSTRACT Due to its outstanding properties, diamond is considered as an ideal material for mechanical and electric applications at high temperatures, voltages, radiation, etc. It is known that femtosecond lasers exhibit extremely high precision and minimized thermal effect in material processing. In this study, a seed-free diamond pattern growth method was developed by patterning silicon substrates using a femtosecond laser before diamond deposition through laserassisted combustion flame synthesis. The resolution of the diamond patterns reaches micro scales. Peak position, full width at half maximum (FWHM), and diamond quality parameter were calculated from Raman spectra. The mechanism of the seed-free diamond growth based on the femtosecond laser patterning was discussed. The influence of substrates surface roughness on the diamond nucleation and subsequent growth was studied, indicating that the nucleation density is proportional to the surface roughness. INTRODUCTION Diamond is expected as a promising material for various applications since it exhibits extreme hardness, chemical and mechanical stability, largest Young’s modulus, and highest thermal conductivity [1]. Such remarkable properties make it extremely attractive for diamondbased micro-electromechanical system (MEMS) applications especially when the devices need to be operated in tough environments [2,3]. However, the realization of various diamond-based devices depends on the approaches of diamond patterning. Currently a great number of efforts have been made to obtain patterned diamond [4-9]. One key challenge to diamond patterning on non-diamond materials is selective diamond growth for the fabrication of diamond-based devices. Nevertheless, current techniques generally require expensive masks and diamond seeds. Since the advance of femtosecond (fs) laser, it has been used for material processing due to fs laser exhibits extremely high precision, minimized thermal effect zone, and versatility [10,11]. In this study, patterned diamond growth on the fs laser processed Si wafers was achieved through laser-assisted combustion synthesis. Fs laser direct-writing (FsLDW) was used for patterning Si substrates before deposition. Diamond patterns of micro- and macro- scales were deposited on the pre-patterned Si substrates without diamond seeding. EXPERIMENTAL PROCEDURES
Substrate pretreatment P-type Si (100) wafers with a dimension of 10 × 10 × 0.6 mm3 were first rinsed by acetone, alcohol, and deionized water, and then mounted on a program controlled stages. A commercial 1kHz amplified Ti:sapphire laser system (Legend F, Coherent Inc.) at 800 nm central wavelength and 120 fs pulse duration was used as th
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