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Published July 15, 1994 | Published
Journal Article Open

Germanium quantum dots: Optical properties and synthesis


Three different size distributions of Ge quantum dots (>~200, 110, and 60 Å) have been synthesized via the ultrasonic mediated reduction of mixtures of chlorogermanes and organochlorogermanes (or organochlorosilanes) by a colloidal sodium/potassium alloy in heptane, followed by annealing in a sealed pressure vessel at 270 °C. The quantum dots are characterized by transmission electron microscopy, x-ray powder diffraction, x-ray photoemission, infrared spectroscopy, and Raman spectroscopy. Colloidal suspensions of these quantum dots were prepared and their extinction spectra are measured with ultraviolet/visible (UV/Vis) and near infrared (IR) spectroscopy, in the regime from 0.6 to 5 eV. The optical spectra are correlated with a Mie theory extinction calculation utilizing bulk optical constants. This leads to an assignment of three optical features to the E(1), E(0'), and E(2) direct band gap transitions. The E(0') transitions exhibit a strong size dependence. The near IR spectra of the largest dots is dominated by E(0) direct gap absorptions. For the smallest dots the near IR spectrum is dominated by the Gamma25-->L indirect transitions.

Additional Information

© 1994 American Institute of Physics. Received 10 November 1993; accepted 23 March 1994. We would like to acknowledge Nicola Hill and Professor K.B. Whaley for lending us their tight binding code for the bans calculations carried out here. We would also like to thank Janet Bowen-Katari for her assistance in performing the XPS. This research was supported by IBM Research. J.J.S. and A.P.A. acknowledge support from the National Science Foundation under Grant No. DMR9057186. J.R.H. acknowledges a fellowship from the Camille and Henry Dreyfus Foundation. A.P.A. wishes to acknowledge the Alfred P. Sloan Foundation Fellowship, J.J.S. wishes to acknowledge an AT&T Predoctoral Fellowship.

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August 22, 2023
August 22, 2023