Azerbaijan National Academy of Sciences Institute of Radiation Problems New Challenges in the European Area: Young Scientist's1st International Baku Forum A MICROSCOPIC INVESTIGATION OF THE -QUANTUM IRRADIATED Pb 1-X Mn X Se EPITAXIAL FILMS Mamishova Rakshana B.Vagabzade 9, Baku, Az BAKI-2013
The aim of the work The search for radiation-resistant materials of various types and the development of new optoelectronic devices operating in the infrared spectrum based on these materials are important challenges facing modern science and technology. Among these materials, AIVBVI compounds and their solid solutions are the particular interest. The presence of ions of heavy metal elements (lead, tin) in the crystal lattice of semiconductors of this type provides the high radiation and thermal stability of the devices prepared on their basis. Far a long time, the above semiconductor compounds and their solid solutions have been extensively used in devices of infrared technology operating in the wavelength range of 3-5 and 8-14mkm 1. Thus, a technique for the preparation of epitaxial films of these materials with a high degree of crystalline perfection on various substrates has been developed in recent years 2-4. In particular, they include epitaxial films of Pb1- xMnxSe solid solutions. The manganese ions in the compositions of these solid solutions impart new properties that are characteristic of semimagnetic semiconductors and offer many possibilities for designing magnetic diodes on their basis that operate in the IR wavelength range of 3-5m
EXPERIMENTAL Pb1-xMnxSe (x=0,01) epitaxial films were prepared on (111) BaF2 substrates by molecular beam condensation at a pressure of 10-4 Pa using a UVN71-P3 standard vacuum system. Synthesized Pb1-xMnxSe (x=0,01) solid solutions were used as the source. The perfection of these films was studied by electron diffraction, electron microscopy, and X-ray diffraction. The electron diffraction pattern of the reflections from the Pb1-xMnxSe films was derived using an EMR-100 electron diffractograph and interpreted to determine the cell parameter (a=6,11A0). According to the developed technique using an additional source of Se, n-and p-type epitaxial films with a cubic structure (a=6,11A0), a thickness of 0,5-1m, a high degree of crystalline perfection (W1/2= ), and high electro physical parameter (n,p(77K) = (2,5- 3)104 cm2/Vs)) were grown. The electro physical parameters (conductivity, Hall voltage) of the films prepared on dielectric substrates were measured by the potentiometric method in a constant magnetic field of 2500 oe in a cryostat evacuated to 210-4 mmHg at the boiling point of liquid nitrogen(77 K). The resulting samples were exposed to a dose of D = 5-35 kGy with a Co60 isotope source. The absorbed dose rate og the source was dD/dt=0,40 Gy/s. the surfaces of the epitaxial films before and after their exposure to the gamma radiation were studied using an SZMU-L5 atomic force microscope (AFM). 3D images of the surfaces of the films, their histograms, and their Fourier spectra were obtained. The conductivity inversion in the irradiated samples was monitored by microscopic and electro physical methods.
Electron diffraction pattern of the Pb 1-x Mn x Se (x=0,01) epitaxial films
3D AFM images of the surface of the n-type Pb 1-x Mn x Se (x=0,01) epitaxial films before(a) and after exposure to gamma radiation at D = 10(b) and D = 25(c) kGy ab c
3D AFM images of the surface of the p-type Pb 1-x Mn x Se (x=0,01) epitaxial films before(a) and after exposure to gamma radiation at D = 10(b) and D = 25(c) kGy c ab a b
Histograms of the AFM images of the surface of the n-type Pb 1-x Mn x Se(x=0,01) epitaxial films before(a) and after exposure to gamma radiation at D = 10(b) and D = 25(c) kGy a b c
Histograms of the AFM images of the surface of the p-type Pb 1-x Mn x Se(x=0,01) epitaxial films before(a) and after exposure to gamma radiation at D = 10(b) and D = 25(c) kGy c ab c
Fourier spectra of the p-type Pb 1-x Mn x Se(x=0,01) epitaxial films before(a) and after exposure to gamma radiation D = 25(c) kGy
CONCLUSIONS Thus, it is shown that the AFM method can be used to study the morphological changes in the surface and postirradiation effects in lead manganese selenide epitaxial films. 3D surface images and their histograms of the original n-and p-type Pb1-xMnxSe (x=0,01) epitaxial films and the samples exposed to gamma radiation(D = 5-35 kGy ) are derived. It is found that the exposure of lead manganese selenide epitaxial films to low doses of -rays( D = 5-35 kGy ) will make possible to change the conductivity type in these samples. The electrophysical data confirm the features of the behavior of the radiation –structured films observed in microscopic measurements. By varying the gamma-radiation dose, it is possible to control the conductivity type inversion and prepare radiation –structured epitaxial films with desired properties.