Silicon Nanoparticle Synthesis Using Constricted Mode Capacitive Silane Plasma
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Silicon Nanoparticle Synthesis Using Constricted Mode Capacitive Silane Plasma A. Bapat1, Ying Dong3, C. R. Perrey2, C. B. Carter2, S.A.Campbell3, and U. Kortshagen1 1 Depatment of Mechanical Engineering 2 Department of Chemical Engineering and Materials Science 3 Department of Electrical and Computer Engineering The University of Minnesota, Minneapolis, MN 55455 USA ABSTRACT Crystalline semiconductor nanoparticles are of interest for a variety of electronic and opto-electronic applications. We report experimental studies of the synthesis and characterization of crystalline silicon nanoparticles using a constricted-mode capacitive RF plasma in continuation of results reported earlier from an RF inductively coupled plasma [1]. The constricted-mode discharge is based on a thermal plasma instability yielding a high-density plasma filament, which rotates at a high frequency. Silane is dissociated, leading to particle nucleation and growth. Particles are extracted by passing the particle-laden gas through an orifice to form a beam and collected by inertial impaction. We are able to reproducibly synthesize highly oriented freestanding single-crystal silicon nanoparticles. Monodisperse particle size distributions centered at a 35nm particle diameter with a geometric standard deviation of 1.3 are obtained. Transmission electron microscope (TEM) studies show uniformly shaped cubic particles. Selected-area electron diffraction patterns indicate the particles have the diamond-cubic silicon structure. To study the electrical properties of these particles, metal-semiconductor-metal structures were fabricated and analyzed. INTRODUCTION Nanoparticles have attracted significant attention from researchers in a variety of disciplines, due to a wide array of potential applications in the fabrication of nanostructured materials and devices. Silicon nanoparticles are of special interest due to their potential for photoluminescence-based devices [2], doped electroluminescent light emitters [3], memory devices [4] and microelectronic devices such as diode and transistor. Different methods have been used to synthesize freestanding silicon nanoparticles such as laser pyrolysis of silane [5], laser ablation of a silicon target [6], evaporation of silicon [7] or gas discharge dissociation of silane [8,9]. While many applications require silicon nanoparticles < 10 nm, applications for electronic devices such as transistors may require larger particles of several tens of nanometer in order to be compatible with current lithography capabilities. Amorphous and polycrystalline particles in this size range can easily be produced using argon-silane discharges [10,11]. However, such particles are not suitable for device applications, which often require single crystal particles. Single nanocrystal particles have higher carrier velocities due to the absence of grain boundaries or defects leading to potentially better performance. Hence, a reproducible, reliable method for generating monodisperse, single-crystal nanoparticles is highly desirab
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