Istraživanje utjecaja plastične deformacije na binarne teluride

master's thesis

• Title (english): Investigation of the influence of plastic deformation on binary tellurides
• Author: Jakov Budić
• Mentor: Damjan Pelc (mentor)
• Committee member: Damjan Pelc (predsjednik povjerenstva)
• Committee member: Zoran Rukelj (član povjerenstva)
• Committee member: Miroslav Požek (član povjerenstva)
• Committee member: Mihael Srđan Grbić (član povjerenstva)
• Committee member: Danko Radić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2024-09-16, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Provedena su mjerenja NMR rezonantne frekvencije i spin-rešetka relaksacijskog vremena jezgre 207Pb u ovisnosti o temperaturi na monokristalnom uzorku olovova telurida (PbTe). Napravljena su i transportna mjerenja otpora i Hallova efekta. Mjerenja su provedena na netaknutom uzorku te su ponovljena nakon plastične deformacije iznosa 3 %. NMR pomak u nedeformiranom uzorku ne pokazuje značajnu temperaturnu ovisnost. Nakon deformacije, dolazi do pomaka rezonantne frekvencije za iznos reda veličine 0.1 %, no temperaturna je ovisnost i dalje vrlo slaba. Spin-rešetka relaksacijsko vrijeme T1 u nedeformiranom uzorku prati temperaturnu ovisnost za poluvodiče. Vrijeme T1 nakon deformacije smanjuje se i pokazuje metalno ponašanje opisano Korringinom relacijom. Transportna mjerenja otpora prije i poslije deformacije pokazuju kvadratnu ovisnost o temperaturi (R ∝ T 2 ), bez aktivacije na nižim temperaturama. Deformirani uzorak ima znatno veći rezidualni otpor koji ne teži u nulu sa smanjenjem temperature. Porast otpora s temperaturom blaži je u deformiranom uzorku u odnosu na nedeformirani. Mjerenjem Hallova koeficijenta, koji je pozitivnog predznaka, utvrđujemo da gustoća nosilaca naboja (šupljina) ne ovisi značajno o temperaturi. U deformiranom uzorku iznos Hallova koeficijenta smanjuje se, dakle gustoća nosilaca naboja je veća. Plastična deformacija monokristalnog uzorka čistog PbTe, na temelju mjerenja nuklearne magnetske rezonancije i transportnih mjerenja, uzorak čini boljim metalom.

Abstract (english)

NMR resonant frequencies and spin-lattice relaxation times of nucleus 207Pb were measured as a function of temperature on a single crystal sample of lead telluride (PbTe). Transport measurements of resistance and Hall effect were also performed. The measurements were carried out on a pristine sample and repeated after plastically deforming it by 3 %. The NMR shift in the undeformed sample does not show significant temperature dependence. After deformation, there is a change in the resonant frequency by an order of magnitude 0.1 %, but the temperature dependence remains very weak. The spin-lattice relaxation time T1 in the undeformed sample follows the temperature dependence typical for semiconductors. The T1 time decreases after deformation and shows metallic behavior described by the Korringa relation. Transport measurements of resistance before and after deformation show a quadratic temperature dependence (R ∝ T 2 ), without activation at lower temperatures. The deformed sample has a significantly higher residual resistance that does not tends to zero as the temperature decreases. Increase of resistance with temperature is more gradual in the deformed sample compared with the undeformed one. By measuring the Hall coefficient, which has a positive sign, it is determined that the charge carrier (holes) density does not significantly depend on temperature. In the deformed sample, the Hall coefficient decreases, indicating that the charge carrier density is higher. Plastic deformation of the single crystal sample of pure PbTe, based on nuclear magnetic resonance and transport measurements, makes the sample a better metal.

• Keywords: olovov telurid (PbTe); plastična deformacija; nuklearna magnetska rezonancija; transportna svojstva; Hallov efekt
• Keywords (english): lead telluride (PbTe); plastic deformation; nuclear magnetic resonance; transport properties; Hall effect
• Language: croatian
• URN:NBN: urn:nbn:hr:217:077017
• Study programme: Title: The University Integrated Undergraduate and Graduate Programme in Physics; Research Physics; specializations in: Research Physics; Course: Research Physics; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: sveučilišni magistar fizike (sveučilišni magistar fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Embargoed access; Embargo expiration date: 2025-09-16
• Created on: 2025-01-31 08:51:04