CC BY
20LD-O-5
Laser Induced Heating of Germanium Nanostructures
A.V.Pavlikov1'2, A.M.Sharafutdinova1, S.N.Bokova-Sirosh3, A.M.Rogov4, A.L.Stepanov4
1 - Faculty of Physics, M.V. LomonosovMoscow State University, Leninskie Gory, Moscow 119991, Russia 2-NationalResearch Centre "KurchatovInstitute", Kurchatov sq., 1, Moscow, 123182, Russia 3-General Physics Institute of Russian Academy of Sciences, Moscow, 119991, Russia. 4-Zavoisky Physical-Technical Institute, FCR Kazan Scientific Center of RAS, Kazan, 420029, Russia
pavlikov@physics. msu. ru
Raman spectroscopy is a widely used method of structural diagnostics. Spontaneous Raman scattering measurements are carried out using cw lasers. Excitation of bulk materials rarely leads to their significant heating, but nanostructured materials can be locally heated up to hundreds of degrees due to the action of exciting laser radiation [1,2]. Strong heating manifests itself in an additional shift of the peak in the Raman scattering spectrum. Heating effect may be explained by low thermal conductivity of porous nanostructures. Unlike porous Si and Ge nanostructures obtained by high-temperature synthesis, Ge nanowires grown by electrochemical deposition from aqueous solutions can crystallize under the action of exciting radiation [3,4].
In this work we present Raman investigation of nanoporous Ge layers formed by implantation with Ag+ and Cu+ at energies E = 30 and 40 keV and doses from 9.3 * 1016 to 1.5 * 1017 ion/cm2. To study the morphology of the formed implanted layers, micrographs were obtained using a high-resolution scanning electron microscope Merlin. Raman studies were carried out on Horiba LabRAM HR-800 and HORIBA LabRAM HR Evolution UV-VIS-NIR-Open micro-Raman spectrometers. Helium-neon (He-Ne) (X= 632.8 nm), Nd:YAG (X= 532.0 nm) and argon (Ar+) (X= 488.0 nm) lasers with a maximum power of 6 mW, with a minimum spot radius of 3 ^m, were used as the exciting radiation.
It was established that implanted Ge nanostructures were amorphous. Irradiation of nanostructures by exciting lasers with an intensity exceeding threshold value leads to heating and subsequent local crystallization of the irradiated regions. The dependence of the crystallization thresholds on the conditions of ion implantation and the wavelength of the probe laser was found. Using the Stokes to anti-Stokes ratio, the local heating temperature was estimated. The results obtained will help to evaluate the thermal conductivity of the nanoporous layers. Such Ge structures can have potential application in thermoelectric elements.
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