Ge Nanocrystal Formed Directly by High-Dose-Ion-Implantation and the Related UV-VIS Photoluminescence
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R9.15.1
Ge Nanocrystal Formed Directly by High-Dose-Ion-Implantation and the Related UV-VIS Photoluminescence Yingqiu Zeng1, Tiecheng Lu1,5*, Ping Zou2, Sha Zhu3, Lumin Wang3, Liru Shen4 1 Department of Physics, Sichuan University, Chengdu 610064, P.R.China Key Lab of Irradiation Physics &Technology(Sichuan University),Ministry of Education, P.R. China 2 Analytic and Testing Center, Sichuan University, Chengdu 610064, P. R. China 3 Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA 4 Southwest Academy of Physics, Chengdu 610041, P.R.China 5 International Center for Material Physics, Chinese Academy of Sciences, Shenyang 110015,P. R. China ABSTRACT The investigation of nanocrystalline Ge (nc-Ge) directly prepared with high dose Ge ion implantation of 1×1016, 1×1017, 5×1017 and 1×1018cm-2 respectively without subsequent annealing is presented in this paper. The specimens were measured by means of GIXRD, LRS and PL. The results show the nc-Ge, which possesses strong compressive stress, can be fabricated when the implanting dose of Ge ions is over the threshold dose～1×1017cm-2. The content and size of nc-Ge will enlarge with increasing dose. The nc-Ge formation mechanism may be the Ge atoms in the amorphous Ge (a-Ge) clusters, which are formed through the aggregation of implanted Ge ions, obtain energy from the instant local annealing zone induced by the incident Ge ion and reconstruct to nc-Ge existing in a-Ge clusters. The PL results indicate the strong PL peaks centered at about 295, 400 and 570 nm can be observed in implanted samples. The intensity of these PL peaks increases with increasing dose. The related PL mechanism in Ge-ion-implanted SiO2 film has also been discussed. INTRODUCTION Ge and Si nanocrystals have been attracting visible photoluminescence and electroluminscence [1-5] can be emitted from them efficiently. The PL is attributed to a quantum confined effect of exciton [4] and /or some defect centers [3]. However, the origin has not yet been clarified. So far, papers about the methods fabricating nc-Ge embedded in SiO2 film reported that nc-Ge would not be precipitated until annealed at over 400℃ [6-11]. Unfortunately, for ion implantation, ion implantation dose is usually so low, ~1017cm-2, as to induce low concentration of nc-Ge and low photoluminescence intensity. In addition, some novel phenomena and properties induced by high dose implantation are not clarified. In this paper, a novel phenomenon of nc-Ge directly formed by ion implantation without subsequent annealing and the related UV-VIS PL is reported.
R9.15.2
EXPERIMENTAL DETAILS In this work, SiO2 films of 500nm thick thermally grown on four p-type Si wafers by dry-wet-dry oxidation at 1180℃ were used for the matrix. The Ge ions were implanted into SiO2 films by JZD-800 multi-functional ion implantation machine with the dose of 1×1016, 1× 1017, 5×1017 and 1×1018cm-2 respectively, flux of about 7×1013 cm-2 s-1 and energy of 40 keV. In order to keep the temperature of matrix
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