Laser Cleaning of Nanoparticles from Solid Surfaces
- PDF / 1,348,381 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 50 Downloads / 311 Views
Laser Cleaning of Nanoparticles From Solid Surfaces Y.F. Lu, W.Y. Zheng, L. Zhang, B. Luk'yanchuk, W.D. Song, W.J. Wang, M.H. Hong, and T.C. Chong Laser Microprocessing Laboratory, Department of Electrical Engineering and Data Storage Institute, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Tel: (65)8742118, Fax: (65)779-1103 , Email: [email protected] ABSTRACT The experimental analysis of dry laser cleaning efficiency is done for certified spherical particle (SiO2, 5.0, 2.5, 1.0 and 0.5 !m) from different substrates (Si, Ge and NiP). The influence of different options (laser wavelength, incident angle, substrate properties, i.e. type of material, surface roughness, etc.) on the cleaning efficiency is presented in addition to commonly analyzed options (cleaning efficiency versus laser fluence and particle size). Found laser cleaning efficiency demonstrates a great sensitivity to some of these options (e.g. laser wavelength, angle of incidence, etc.). Partially these effects can be explained within the frame of the Mie theory of scattering. Other effects (e.g. influence of roughness) can be explained along the more complex line, related to examination of the problem “particle on the surface” beyond the Mie theory. 0.5 µm spherical silica particles were placed on Silicon (100) substrate. After laser irradiation with a 248 nm KrF excimer laser, hillocks with size of about 100 nm were obtained at the original position of the particles. Mechanism of the formation of the sub-wavelength structures were investigated and found to be the near-field optical resonance effect induced by particles on surface. Theoretical prediction of the near-field light intensity distribution was presented, which was in agreement with the experimental result. INTRODUCTION Recently, laser-particle-surface interaction attracts a lot of concerns in experimental and theoretical studies. There are three main impetuses behind this problem: first, as the dimension of active elements shrinks drastically in IC and high-density hard disk manufacturing, even a submicron particle may induce fatal damages to the whole system. On the other hand, because the inertial force m !x! contains mass m " R 3 and the adhesion force Fadh " R , the necessary acceleration is !x! " R # 2 (R is radius of the particle) [1]. Typically, it is about 107 times higher than the gravity force for a 1 !m particle [2]. Traditional cleaning methods, such as hydrodynamic jet and ultrasonic vibration, can not remove small particles efficiently. Fortunately, pulsed laser heating of the absorptive particle or substrate can produce such high acceleration [3-26]. Second, due to the simplicity of the laser-particle-surface system, it can be applied in the study of the particle adhesion and deformation on solid substrate, which is the basis of many cross-discipline subjects [27-31]. Third, the fascinating physics arises in laser cleaning problem, the latest are e.g. effects, related to near-field focusing of radiation by particle with size comparable with laser
Data Loading...
