Dr. Arturs Medvids, Professor, Riga Technical University, Latvia

Arturs Medvids, optics and spectroscopy physicist, graduated from Physics department of Kiev State University, Ukraine, in 1968. He worked for Institute of Semiconductor Physics of Ukrainian Academy of Sciences 1959-1969. In 1994 obtained the degree Dr. habil. Phys., with specialization: Solid State Physics at Latvian University, Riga. Since 1989 he has been the head of Laboratory of Semiconductor Physics at Riga Technical University and since 1995 - Professor at the Institute of Technical Physics of Riga Technical University. In 2001 and 2017 he worked in Japan as an invited professor in Shizuoka University. He was awarded the title of Honourable guest professor of Shizuoka University, Japan, in 2009, 2014 and 2016. He has published more than 575 scientific publications: papers, conferences proceedings, books and patents. He was an Invited speaker at the 12th International Conference on Solid Films and Surfaces, 2005, in Hamamatsu, Japan, at the International conference, Villa Conferences on Energy, Materials and Nanotechnology, 2011, in Las Vegas, USA, at 1st International Conference on Nanostructured Materials and Nanocomposites, 2009, in Kerala, India, at 14th and 15th International Symposium on Ultrafast Phenomena in Semiconductors, 2010, 2013, in Vilnius, Lithuania, at SPIE Conference Advanced Optical Materials and Devices, 2011, in Vilnius, Lithuania, at 11th International Young Scientists Conference SPO-2010 in Kiev, Ukraine, at 5th Baltic Conference on Silicate Materials, 2011, in Riga, Latvia and Plenary speaker at The International Conference Nanomaterials: Applications and Properties, 2012, in Alushta, Ukraine, at Energy Materials Nanotechnology East Meeting, 2014, Beijing, China, Plenary Lecturer at the 8th International Conference on Materials Science and Condensed Matter Physics, 2016, Chisinau, Moldova, and Keynote Speaker at the 19th Nano Congress for Next Generation, 2017, in Brussels, Belgium.

Speech Title: Control of Micro Hardness in Semiconductor by Laser Radiation: from Elastic till Plastic Deformation

Abstract: Mechanical stress plays the main role on duration of performance of semiconductor devices and microprocessors. The cause of the stress may be different, depending on manufacture technology performance conditions and structure of the device. So, for example, design of the heterostructure of photon detector or diode is characterized by mechanical stress on the interface due to mismatch of the crystalline lattice semiconductor components or difference in thermal expansion coefficients. Therefore, laser method for control of mechanical stress on nano level is proposed. It was found that strongly absorbed Nd:YAG laser radiation (second harmonica of Nd:YAG laser wave lings 532nm, pulse duration 6ns, maximal laser intensity 10 MW/cm2) leads to a non-monotonous dependence of micro hardness of p-Si(B) and n-type Si(P) crystals on laser radiation. This dependence is characterized by two maxima for p-Si and one maximum for n-Si crystals. In both cases the increase of micro hardness at higher laser intensity is explained by formation of mechanically compressed layer at the irradiated surface due to concentration of the interstitial atoms at the surface of Si crystal in temperature gradient field. The decrease of micro hardness is explained by formation of nano-cones on the irradiated surface of crystal which was observed in Si, Ge, GaAs and CdTe using atomic force microscope.