Transport properties of semiconductor nanostructures

Slunjski, Robert (2014) Transport properties of semiconductor nanostructures. Doctoral thesis, Faculty of Science > Department of Physics.

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Abstract

In the scientific community semiconductor nano structures are very active field of research becauseof the possibility to design materials with specific electrical properties. Such structures have agreat potential for the use as new semiconductor devices, sensors, photovoltaics etc. Despitemany years of active research and many published papers it is still a big challenge to producenano structures in a reliable and economical manner with exact size and small number of defects.In this doctoral thesis we applied magnetron sputtering technique to produce semiconductornano structures of Si and Ge in difeerent environments of SiO_2, Si_3N_4 and SiC. It was foundthat the temperature annealing process at 1050°C for Si and 700°C for Ge during 1h in theatmosphere of N_2 is ideal for creating the nano crystalline Si and Ge. X-ray diffraction revealsthe crystallinity of produced nano material and with the luminescence in the visible range thecapture of photons in nano crystals is demostrated.The electrical transport properties are studied using MOS structures in which the oxide layeris made with the semiconductor nano material of Si and Ge. The interface defect density ofMOS structures shows, a quality of samples with D_it ~ 10^12cm^-2eV^-1. The charge capture innano crystals is shown with capacitive techniques and is most pronounced for a samples withnano crystals of Ge size of 2.5 nm embedded in multilayer oxide structure.The most dominant way of current transfer through matrix with nano crystals when MOSstructure is forward polarised is the space charge limited current (SCLC) for high voltages andthe ohmic current for low voltages. For thicker samples the ohmic current is dominant way ofcharge transfer and for thinner samples the SCLC current is the dominant way of charge transferin any voltage regime. Measurement under light excitation showed us that the current is gettingbigger and the type of conductivity didn't change except for some samples in which the change ofdensity of defect states was noticed. The samples with nano-structure of Si in SiO_2 showed thephotovoltaic effect after excitation by light source which is interesting for using nano-structuresfor photovoltaic applications.

Item Type: Thesis (Doctoral thesis)
Keywords: quantum dots ; nanocrystalline Si i Ge ; MOS structure SCLC current ; magnetron sputtering ; Raman
Supervisor: Pivac, Branko
Date: 4 April 2014
Number of Pages: 128
Subjects: NATURAL SCIENCES > Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 10 Apr 2014 14:30
Last Modified: 10 Apr 2014 14:30
URI: http://digre.pmf.unizg.hr/id/eprint/798

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