Reflection Absorption Infrared Spectroscopy Study on the Spontaneous Formation of Erbium Monoantimonide Nanoparticles on
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Reflection Absorption Infrared Spectroscopy Study on the Spontaneous Formation of Erbium Monoantimonide Nanoparticles on Indium Antimonide Surfaces Takehiro Onishi1, Andrew J. Lohn1,2, Elane Coleman3, Gary S. Tompa3 and Nobuhiko P. Kobayashi1,2; 1 Baskin School of Engineering, University of California Santa Cruz, Santa Cruz, California; 2 Nanostructured Energy Conversion Technology and Research (NECTAR), Advanced Studies Laboratories NASA Ames Research Center, Moffett Field, California; 3 Structured Materials Industries, Piscataway, New Jersey. ABSTRACT We describe an ex-situ monitoring technique for a small amount (~30 mono-layers) of erbium monoantimonide (ErSb) deposited on an indium antimonide (InSb) epitaxial layer prepared on InSb(100) substrates by metal organic chemical vapor deposition (MOCVD). Our objective is to improve thermoelectric properties of nanocomposites that employ nanometer size semi-metallic ErSb particles (ErSb nanoparticles) embedded in ternary group III-V compound semiconductor host materials such as indium gallium antimonide (InGaSb) and indium antimonide arsenide (InSbAs). The formation of ErSb nanoparticles embedded in a host material is spontaneous and needs to be carefully controlled to tune the size and volume density of the ErSb nanoparticles. We used an ex-situ monitoring technique based on glancing-angle infraredabsorption, reflection absorption infra-red spectroscopy (RAIRS), to study the formation of ErSb nanoparticles to correlate the amount of delivered ErSb and surface morphology of the surface of InSb covered with ErSb. INTRODUCTION In the quest of developing a route to optimize physical properties such as Seebeck coefficient, electrical conductivity, and thermal conductivity of bulk group III-V compound semiconductors with the view toward efficient thermoelectric power generation devices, we have been developing “nanocomposites” in which semi-metallic rare-earth compound (e.g., erbium monoantimonide) in the form of nanometer-scale particles are embedded in a ternary group III-V compound semiconductor host. Combining dissimilar materials at nanometer-scale within a bulk material often leads to unique modifications in physical properties of the resulting bulk material. The formation of semiconductor quantum dots such as indium arsenide within a gallium arsenide host is driven by atomistic surface processes under the influence of mechanical stress caused by mismatch strain between two dissimilar materials (i.e., the Stranski-Krastanov mechanism [1]). A solid surface acts as a growth front where it meets a liquid or vapor phase. The process of crystal growth is catalyzed by physical and chemical characteristics of a surface on which various atomistic processes progress simultaneously. Our goal is to grow semi-metallic ErSb nanoparticles embedded within ternary group IIIV compound semiconductor host materials such as indium gallium antimondes (InGaSb) and indium antimonide arsenide (InSbAs). This unique combination of two dissimilar materials is a new approach for synthesizing na
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