Synthesis of Light Emitting Ge Nanocrystals by Reactive RF Sputtering
In this work we report the results of the synthesis, structural and optical characterization of SiO2/Ge/SiO2 heterostructures by reactive RF sputtering. The SiO2 films were grown by reactive sputtering employing a plasma mixture of oxygen and argon. The Ge layer was grown employing an Ar atmosphere. The samples were prepared on p-type Si (1 1 1) substrates by reactive sputtering. The effect of the partial pressure of oxygen on the electronic properties of the heterostructure is reported. Structural characterization was carried out by grazing angle X-ray difraction. Surface roughness was quantified by atomic force microscopy. The presence of Ge nanocrystals (Ge-NCs) was evidenced by X-ray diffraction. The vibrational properties were studied by Raman spectroscopy. The Raman spectra showed modes associated to germanium indicating the formation of low dimensionality germanium particles embedded within a SiO2 matrix. Photoluminescence emission is observed around ~1.7 eV and it is associated to the quantum confinement of carriers in Ge-NCs. Ohmic contacts were deposited using a van der Pauw geometry employing an a AuSb alloy for the contacts. Temperature dependent Hall (T-Hall) measurements were done between 35 K and 150 K, using the van der Pauw method. The results indicated low resistivity values that could be explained due to some variable range hopping conduction mechanism.
W. Jantsch and F. Schäffler
A. Hernandez-Hernandez et al., "Synthesis of Light Emitting Ge Nanocrystals by Reactive RF Sputtering", Solid State Phenomena, Vols. 178-179, pp. 61-66, 2011