Nanostructured surfaces 

Morphological changes of structures with surface quantum dots under the gamma irradiation
P.Moskvin1, L.Rashkovetskyi2, O.Strilchuk2, K.Svezhentsova2, V. Kryzhanivskyy1

1StatеUniversity “Zhytomyrskapolitechnika”, 103 Chudnivska str.,10005, Zhytomyr, Ukraine E-mail: moskvinpavel56@gmail.com
2V.Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 41, Prospect Nauky, 03680, Kyiv, Ukraine E-mail: ostrilchuk@gmail.com 

The AFM image of the In0.4Ga0.6As/GaAs structures surface with quantum dots (QD) before and after their interaction with -irradiation within 105 - 108 rad was analyzed. The influence of -radiation on the geometric parameters of nanorelief for QD structures was established. The MFA method [1] was used to quantify the variation of the geometric parameters of surface nanoforms depending on the dose of -irradiation. The dependences of the Renyi’s numbers and fractal ordering parameters on the irradiation dose were found. It is shown that with increasing radiation dose there is a blurring (destruction) of interfaces of QD, which correlates quantitatively with a decrease in the values of Renyi’s numbers for surface area and volume of surface nanoforms. The study of the width of multifractal spectra (fractal ordering parameter) showed the rearrangement of the fractal structure of the surface as different doses of radiation exposed to it.
The obtained results are in good agreement with the spectral dependences of initial and irradiated structures with surface In0.4Ga0.6As/GaAs QDs [2]. At low irradiation doses (105 rad) there is an increase in the intensity of PL caused by an improvement in the crystal quality of the structure (the "low doses" effect). Increasing the radiation dose to 106 -107 rad leads to the accumulation of radiation defects and the appearance of radiation-induced defect levels near the QDs/wetting layer interfaces, which are an additional channel for transferring carriers from the wetting layer to QDs, and causing a significant magnification in PL intensity. Increasing the radiation dose to 108 rad enhances the role of diffusion processes increases the mobility of both growth defects and radiation-stimulated defects, which leads to the destruction of QD boundaries, resulting in a sharp decrease or disappearance of PL intensity.. 

1. Moskvin P., Kryzhanivskyy V., Rashkovetskyi L., Lytvyn P. // J.  Crystal Growth. -2014.-404. -P.204-209. 
2. Maslov V., Venger E., Rudko G., Gule E., Strilchuk O. // E-MRS Spring Meeting 2018, June 18-22, Strasburg, France. Symposium K, P.K-17.