Utjecaj kristalnih defekata na fazna pobuđenja u valovima gustoće naboja

doctoral thesis

• Title (english): Influence of crystal defects on phase excitations in charge density waves
• Author: Damir Dominko
• Mentor: Damir Starešinić (mentor)
• Committee member: Slaven Barišić (predsjednik povjerenstva)
• Committee member: Damir Starešinić (član povjerenstva)
• Committee member: Silvia Tomić (član povjerenstva)
• Committee member: Ivo Batistić (član povjerenstva)
• Committee member: Mario Basletić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2012-09-25, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics
• Universal decimal classification (UDC): 53 - Physics

Abstract

U ovoj disertaciji izučavan je utjecaj defekata na prijelaz u stanje vala gustoće naboja (VGN) i svojstva niskoenergetskih pobuđenja faze VGN-a, u ozračenim i dopiranim uzorcima VGN sistema o-TaS3. Smrzavanje fazne dinamike na temperaturi TG, kao dio složenih svojstva niskoenergetskih pobuđenja u VGN sistemima, posljedica je vezanja VGN-a sa defektima i slobodnim nosiocima naboja. Predloženi kriterij smrzavanja1, prema kojem je TG određena brojem slobodnih nosilaca naboja u domeni korelacije faze VGN-a je, kao glavni motiv istraživanja, u ovoj disertaciji potvrđen na uzorcima sa širokim rasponom udjela defekata. Transportna i dielektrična mjerenja, u širokom temperaturnom, naponskom i frekventnom području, pokazuju da defekti uzrokuju promjenu polja praga, niskofrekventne dinamike i dielektrične konstante, ali ne i linearne vodljivosti iznad TG, dok je ispod TG opažena samo promjena u linearnoj vodljivosti. Pokazano je da je zapinjanje faze u ozračenim uzorcima iznad TG jakog, a u dopiranim slabog karaktera. Ispod TG javlja se nelinearni kanal vodljivosti skokova varijabilnog dosega.

Abstract (english)

In this dissertation the influence of defects on the transition to charge density wave (CDW) state and properties of low energy CDW phase excitations has been studied in irradiated and doped samples of CDW system o-TaS3. Phase dynamics freezing at a temperature TG, as a part of complex properties of low energy excitations in CDW systems, is a consequence of CDW coupling to defects and free charge carriers. As the main motive of this research, proposed freezing criterion1 (according to which TG is determined by a number of free charge carriers within a CDW phase correlation domain) has been confirmed in samples with a wide range of defects. Transport and dielectric measurements, over a wide temperature, voltage and frequency range, show that the defects influence the threshold field, low-frequency dynamics and dielectric constant, but not the linear conductivity above TG, while below TG only an influence on the linear conductivity has been observed. Strong and weak phase pinning mechanisms above TG are confirmed in irradiated and doped samples, respectively. Below TG variable range hopping type of nonlinear conductivity channel appears.

• Keywords: val gustoće naboja; kristalni defekti; staklasti prijelaz; dielektrična spektroskopija; transport
• Keywords (english): charge density wave; crystal defects; glass transition; dielectric spectroscopy; transport
• Language: croatian
• URN:NBN: urn:nbn:hr:217:472492
• Study programme: Title: Physics; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika (doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika)
• Type of resource: Text
• Extent: 146 str.
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-08-23 10:18:52