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Dobijanje i karakterizacija 2D i 3D funkcionalnih materijala iz klase halkogenida dopiranih srebrom

Preparation and characterisation of 2D and 3D functional materials from the group of chalcogenides doped with silver

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Author
Čajko, Kristina
Mentor
Lukić-Petrović, Svetlana
Sekulić, Dalibor
Committee members
Petrović, Dragoslav
Lukić-Petrović, Svetlana
Sekulić, Dalibor
Gut, Imre
Stojanović, Goran
Metadata
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Abstract
Predmet istraživanja ove doktorske disertacije su bila halkogenidna stakla iz sistema Agx(As40S30Se30)100–x (x = 0, 0.5, 1, 2, 3, 4, 5, 10, 12, 13, 15 at. % Ag) – 3D forma i tanki filmovi preparirani iz prethodno sintetisanih stakala (x ≤ 5 at. % Ag) – 2D forma. Utvrđena je oblasti amorfnosti u faznom dijagramu po odabranom preseku.  Ispitivan je uticaj procentualnog udela srebra  na  fizičke  karakteristike sintetisanih stakala i prepariranih tankih filmova koje su  od  značaja  za  primenu  ovakvih  materijala. Izvršena je karakterizacija električnih,  optičkih, strukturnih  i  termičkih  osobina  na  osnovu  kojih  su izvedeni  zaključci  o  uticaju  i  modifikaciji  strukture As40S30Se30 halkogenidne matrice usled inkorporacije atoma srebra. Strukturna analiza ispitivanih sastava je potvrdila homogenost uzoraka sa manjom koncentracijom srebra (x ≤ 5 at. %  Ag), dok je  kod uzoraka sa većim procentualnim udelom ovog metala (x = 10, 13, 15 at. % Ag) pokazano da postoji fazna separaci...ja. Kod sastava sa x = 13 i 15 at. % Ag potvrđena  je  prisutnost kristalnih centara AgAsSe2. Na osnovu rezultata dobijenih DSC tehnikom, pokazano je da pri zagrevanju balk uzoraka dolazi do delimične kristalizacije koja se odvija zapreminski sa dvodimenzionalnim  i  trodimenzionalnim rastomkristalnih centara. Optička i spektralna ispitivanja su pokazala  da uvođenje  Ag  u  matricu  stakla As40S30Se30  dovodi  do  smanjenja  širine  optički zabranjene zone i kod 3D i 2D uzoraka, kao i da svi sastavi ispoljavaju normalan oblik disperzije indeksa prelamanja. Takođe, rezultati Raman  spektroskopije su ukazali  na  činjenicu  da  inkorporacija  srebra  u strukturnu  mrežu  ispitivanih  stakala  utiče  na formiranje Ag–(S,Se)–As veza, odnosno uzrokuje formiranje novih strukturnih jedinica koje bi mogle uticati na provodljivost ovih sastava.  Merenja električnih karakteristika 3D uzoraka izvršena su u jednosmernom i naizmeničnom režimu i pokazano je da  koncentracija  srebra  ima  značajan  uticaj  na električne  osobine.  Utvrđeni  su  različiti  mehanizmi odgovorni za transport  nosilaca naelektrisanja zavisno od  koncentracije dopanta.  Kompleksni impedansni spektri svih sastava  su  ukazali  na prisustvo temperaturske zavisnosti procesa relaksacije, na ne idealan Debye–vski tip relaksacije, kao i negativni temperaturski koeficijent otpornosti koji je karakterističan za poluprovodnike.

The subject of this dissertation are chalcogenide  glasses from the system Agx(As40S30Se30)100–x (x = 0, 0.5, 1, 2, 3, 4, 5, 10, 12, 13, 15 at. % Ag) – 3D form and thin films prepared from previously synthesised  glasses (x ≤ 5 at. % Ag) – 2D form. The amorphous  area in the phase diagram was determined by the  selected    tie– line. The influence of the silver  percentage on the physical characteristics of the  synthesized glasses and prepared thin films was  investigated due to the importance of such materials  for the application. Characterization of electrical, optical, structural and thermal properties has been performed, based on which conclusions on theinfluence and structure modification of the As40S30Se30  chalcogenide  matrix due to the  incorporation of silver atoms have been derived. Structural analysis of the investigated samples confirmed the homogeneity of samples with a lower silver concentration (x  ≤  5  at.%  Ag),  while  in samples with a higher percentage content o...f  this metal (x = 10, 13, 15 at.% Ag) it was shown that  there was a phase separation. The presence of crystal  centers AgAsSe2 was confirmed in the samples with x = 13 and 15 at. % Ag. Based on the results obtained with the DSC technique, it has been shown that by heating the samples, partial crystallization takes place voluminously, with two–dimensional and three–dimensional growth of crystalline centers.  Opticaland spectral investigations have shown that the introduction of Ag into the glass matrix As40S30Se30 leads to a reduction in the optical band gap in both 3D and 2D samples, and that all compositions exhibit a normal dispersion of index of  refraction. Also, the Raman spectroscopy results pointed to the fact that the incorporation of silver into the structural network of the investigated samples influences the formation of  Ag–(S,Se)–As structures that is, causes the formation of new structural units that could affect the conductivity of these compositions. Measurements of the electrical characteristics of the 3D samples were performed in  DC and AC regime and it was shown that silver concentration has a significant effect on electrical properties. Different mechanisms that are responsible for the transport of charge carriers depending on dopant concentration were determined. The complex  impedance spectra of all compositions indicated the presence of the temperature dependence of the relaxation process, the non–Debye relaxation and the negative temperature coefficient of resistance which is characteristic of the semiconductors.

Faculty:
University of Novi Sad, Faculty of Science
Date:
13-07-2018
Projects:
  • Materials of Reduced Dimensions for Efficient Light Harvesting and Energy conversion (RS-45020)
  • Physics of amorphous and nanostructural materials (RS-171022)
Keywords:
Halkogenidna stakla / Chalcogenide glasses / tanki filmovi / srebro / novi materijali / impedansna spektroskopija / VIS/NIRspektroskopija / skenirajuća elektronska mikroskopija / diferencijalno–skenirajuća kalorimetrija / thin films / silver / new materials / impedance spectroscopy / VIS/NIRspectroscopy / scanning electron microscopy / differential–scanning calorimetry
[ Google Scholar ]
URI
http://nardus.mpn.gov.rs/handle/123456789/9730
https://www.cris.uns.ac.rs/DownloadFileServlet/Disertacija152474491728860.pdf?controlNumber=(BISIS)107274&fileName=152474491728860.pdf&id=11282&source=NaRDuS&language=sr
https://www.cris.uns.ac.rs/record.jsf?recordId=107274&source=NaRDuS&language=sr
https://www.cris.uns.ac.rs/DownloadFileServlet/IzvestajKomisije152474493553080.pdf?controlNumber=(BISIS)107274&fileName=152474493553080.pdf&id=11283&source=NaRDuS&language=sr

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