Influence of Growth Conditions on Amorphous Germanium Films Prepared by Vacuum-Evaporation

Tatsumi, Yukako; Honda, Hirokazu; Ikegami, Kaori; Naito, Shokichi

doi:10.1143/jpsj.56.2977

Cited by 5 publications

(2 citation statements)

References 14 publications

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“…Even if all the Ge in the as-prepared sample is due to the NPs, there is only approximately 35 wt % Ge. As the sample was heated under vacuum to different temperatures, the average diameter of the particle increase and the 300 °C sample showed no electron diffraction and broad amorphous X-ray powder diffraction pattern. ,, The mean particle diameter was 5.1 ± 1.0 nm. The 450 °C sample also shows a broad diffraction pattern and a mean particle diameter of 6.0 ± 1.1 nm.…”

Section: Resultsmentioning

confidence: 97%

Phase Changes in Ge Nanoparticles

2005

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Butyl-capped crystalline germanium (Ge) nanoparticles were synthesized at room temperature in dimethoxyethane by reduction of GeCl 4 with Na(naphthalide) and subsequent reaction with butyl Grignard. The nanoparticles were isolated in hexane and characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), elemental analysis, and X-ray powder diffraction (XRD). The product from this room-temperature reaction was heated under vacuum at temperatures of 200-600 °C at 50 °C intervals. The product obtained from the 300 °C treatment was soluble in hexane, while the products from temperatures greater than 300 °C were not. SAED was consistent with crystalline Ge from the initial synthesis at room temperature and amorphous Ge for the product heated under vacuum to 300 °C. X-ray powder diffraction of the 300 °C product shows the transition from amorphous to crystalline nanoparticles occurring between 550 and 600 °C. TEM shows that the nanoparticles remain dispersed and nonaggregated up to 600 °C. Differential scanning calorimetry (DSC) shows a crystallization exotherm at 561 °C and a melting endotherm at 925 °C for nanoparticles with average diameter of 8 nm.

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Section: Resultsmentioning

confidence: 97%

Phase Changes in Ge Nanoparticles

2005

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“…It is known that physical properties of a-Ge films depend on growth conditions. Tatsumi et al 30 show that a startling range of densities from 2.77 to 5.03 g/cm3 can be explained with two parameters: pressure in the growth chamber and deposition rate. Viscor and Allan31 report that density also depends on the type of substrate.…”

Section: Structural Investigationmentioning

confidence: 99%

X-ray absorption fine-structure study of amorphous germanium under high pressure

Freund¹,

Ingalls²,

Crozier³

1990

J. Phys. Chem.

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1087example, we have not determined yet whether in the process of observing phonon-assisted laser operation macroscopic occupation of a phonon mode occurs and whether we are operating a phonon oscillator. High-pressure measurements, among others, may help resolve these questions. In previous high-pressure measurements on QWHs we (N.H.) with H. Drickamer and our students have been able to probe, because of easily resolved confined-particle exciton states, the "inside" of an energy band and not just the band edges.21 High-Q heat sinking of a QWH and photopumping present an opportunity to observe confined-particle transitions (recombination radiation) and phonon sidebands (not just bulk-(21) Kirchoefer, S. W.; Holonyak, Jr., N.; Hess, K.; Gulino, D. A.; Drickamer, H. G.; Coleman, J. J.; Dapkus, P. D. Appl. Phys. Lett 1982, 40, 821.crystal band-edge processes) and see how they "tune" with pressure. These are experiments worth pursuing. We wish many more vigorous years for Harry Drickamer and the opportunity to do more high-pressure studies with him, including high-pressure versions of the experiments described here. Acknowledgment.We are grateful to John Bardeen for helpful discussions (N.H.) on macroscopic phonon occupation in photopumped QWHs. For technical assistance we thank B. L. Marshall, R. T. Gladin, and B. L. Payne.

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