Nanostructures on semiconductor surfaces applied in microelectronics, super-high density storaging of information, nanophotonics for development of light-emitting devices and for spectroscopy. Therefore it is of a great... [ view full abstract ]
Nanostructures on semiconductor surfaces applied in microelectronics, super-high density storaging of information, nanophotonics for development of light-emitting devices and for spectroscopy. Therefore it is of a great interest to develop new effective methods for obtaining surface structures with characteristic sizes less than 100 nm.
In this work the formation of nanoreliefs on germanium surface is carried out by one laser beam without any optional devices and masks. Such method is called the direct laser nanostructuring [1,2]. Figure 1 shows principle scheme of experimental setup for direct laser nanostructuring. The excimer ArF-laser with a wavelength of 193 nm is the main source of coherent radiation, which is strongly absorbed by most materials. After the necessary preparatory procedures germanium samples were irradiated by 20 nanosecond laser pulses transmitted through the optical system (figure 1).
The analysis of initial and irradiated sample surfaces is carried out by an atomic-force microscope (AFM). AFM-analysis shows the formation of various types of surface micro- and nanostructures in different parts of irradiation zone. For example, figure 2 represents nanostructures in the form of bulbs with rounded peaks with characteristic dimensions along the surface of 40-120 nm and a height of 40-70 nm. They are observed in peripheral low-intensity region of the laser spot and its size makes it possible to use such structures as quantum dots. Figure 3 shows hexa- and pentagonal cells with characteristic dimensions along the surface of 300-500 nm and the height of the edges between the cells of 20-25 nm in the region of "shallow" melt. Figure 4 represents wave-like microrelief in the zone of "deep" melt near the center of laser spot.
Considering experimental data, we propose a classification of surface reliefs, which includes five main types of reliefs characterized by the shape and size of the structures formed, their periodicity and the physical mechanism of the formation of structures in different regions of the irradiation spot.
References:
[1] Mikolutskiy S.I., Khomich V.Yu., Shmakov V.A., Yamshchikov V.A., Nanotechnologies in Russia, 6 (2011) 733.
[2] Ganin D.V., Mikolutskiy S.I., Tokarev V.N., Khomich V.Yu., Shmakov V.A., Yamshchikov V.A., Quantum Electronics, 44 (2014) 317.
