Abstract
The visible luminescence from Ge nanoparticles and nanocrystallites has generated interest due to the feasibility of tuning band gap by controlling the sizes. Germanium (Ge) quantum dots (QDs) with average diameter ~16 to 8 nm are synthesized by radio frequency magnetron sputtering under different growth conditions. These QDs with narrow size distribution and high density, characterized using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) are obtained under the optimal growth conditions of 400 °C substrate temperature, 100 W radio frequency powers and 10 Sccm Argon flow. The possibility of surface passivation and configuration of these dots are confirmed by elemental energy dispersive X-ray (EDX) analysis. The room temperature strong visible photoluminescence (PL) from such QDs suggests their potential application in optoelectronics. The sample grown at 400 °C in particular, shows three PL peaks at around ~2.95 eV, 3.34 eV and 4.36 eV attributed to the interaction between Ge, GeOx manifesting the possibility of the formation of core-shell structures. A red shift of ~0.11 eV in the PL peak is observed with decreasing substrate temperature. We assert that our easy and economic method is suitable for the large-scale production of Ge QDs useful in optoelectronic devices.
Highlights
The Ge\Si(100) system among the self-assembled semiconductors nanostructure has generated intense interest since it is the simplest semiconductor hetero-epitaxial system that opened new possibilities for optoelectronic and microelectronic applications
The particle sizes (~8 nm to ~17 nm) estimated from field emission scanning electron microscopy (FESEM) are in conformity with the atomic force microscopy (AFM)
The surface of the Ge quantum dots (QDs) is modeled as covered by thin oxide layers having a thickness of a few nm, and the Ge islands grown at room temperature (RT) are considered to have the thickest oxide layer
Summary
The Ge\Si(100) system among the self-assembled semiconductors nanostructure has generated intense interest since it is the simplest semiconductor hetero-epitaxial system that opened new possibilities for optoelectronic and microelectronic applications. Ge QDs having sizes 8 to 20 nm were prepared by Fahim et al using electron beam evaporation technique, in which the root mean square (RMS) roughness is shown to be highly sensitive to the annealing temperature. Oku et al The PL peaks are related to luminescence that originates from the Ge/GeOx interface and quantum size effect of Ge clusters. They indicated that the formation of the core-shell structure of Ge and Si with oxide layers is the reason for the blue shift of band gap energy [12]. The details of the growth behavior and optical properties are investigated by PL spectroscopy with varying substrate temperature
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