Multifractal analysis of SiO 2 surface embedded with Ge nanocrystal
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ORIGINAL ARTICLE
Multifractal analysis of SiO2 surface embedded with Ge nanocrystal R. P. Yadav1 · V. Baranwal2 · Sunil Kumar3 · A. C. Pandey2,3 · A. K. Mittal4 Received: 29 September 2020 / Accepted: 10 November 2020 © King Abdulaziz City for Science and Technology 2020
Abstract In the present article S iO2/Si layers of thickness 200 nm were implanted with 150 keV Ge ions with different fluences varying from 2.5 × 1016 to 7.5 × 1016 ions/cm2. The implantation-induced disorder was removed via high temperature annealing method in Ar ambience. Transmission electron microscopy (TEM) measurement confirmed the presence of embedded Ge nanocrystals of 5–10 nm size in annealed samples. Topographical studies of implanted as well as annealed samples were captured by the atomic force microscopy (AFM) and parameters such as average roughness and interface width were extracted. Two dimensional multifractal detrended fluctuation analysis (2D-MFDFA) based on the partition function approach was used to study the surfaces of ion implanted and annealed samples. The partition function is used to calculate generalized Hurst exponent with the segment size. A nonlinear variation with moment is observed for generalized Hurst exponents, leading to the multifractal nature. The multifractality of surface is pronounced after annealing for the surface implanted with fluence of 7.5 × 1016 ions/cm2. Keywords Atomic force microscopy (AFM) · Multifractal detrended fluctuation analysis (MFDFA) · Partition function · Hurst exponents · Multifractality · Ion implantation · Ge quantum dots
Introduction Embedded semiconducting quantum dots (QDs) in a thin film dielectric matrix have significant technological applications in various fields such as spintronics, optoelectronics, and photonics. Due to their novel characteristic QDs can be incorporated in semiconductor devices like light emitting diodes (Sabarinathan et al. 2002), lasers (Huffaker et al. 1998), and field effect transistors (Drexler et al. 1994). In recent times, semiconductors QDs have been extensively used in equipments with peculiar uses. Due to high density and low voltage memory devices of QDs a substantial amount of research activities have been performed to study * V. Baranwal [email protected] 1
Department of Physics, Deen Dayal Upadhyay Govt. P.G. College, Saidabad, Allahabad 221508, India
2
Nanotechnology Application Centre, University of Allahabad, Allahabad 211 002, India
3
Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067, India
4
Department of Physics, University of Allahabad, Allahabad 211002, India
the memory effects (Lu et al. 2006). Embedded nanocrystals in dielectric matrix have been widely considered for storing charges in nanocrystal gate memories in non-volatile memory devices (Lu et al. 2006). Furthermore, the smaller band gap of Ge as compared with Si allows rapid write and erase speeds (Baranwal et al. 2008). It can also be utilized for manufacturing infrared detecting devices such as thermistor materials (Baranwal
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