Material Type  

 학위논문

 

0016932358

Date and Time of Latest Transaction  

20240214100447

ISBN  

9798379613389

DDC  

530

Author  

Spitzig, Alyson.

Title/Author  

Using Non-Contact AFM to Study the Local Doping and Damping Through the Transition in an Ultrathin VO2 Film - [electronic resource]

Publish Info  

[S.l.] : Harvard University., 2023

Publish Info  

Ann Arbor : ProQuest Dissertations & Theses, 2023

Material Info  

1 online resource(136 p.)

General Note  

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

General Note  

Advisor: Hoffman, Jennifer.

학위논문주기  

Thesis (Ph.D.)--Harvard University, 2023.

Restrictions on Access Note  

This item must not be sold to any third party vendors.

Abstracts/Etc  

요약Bulk VO2 undergoes an insulator-to-metal transition (IMT) with up to five order of magnitude change its resistivity at 340 K. However, when VO2 is deposited as a film on a substrate, the strain from the substrate can alter the IMT temperature, resistivity ratio, and hysteresis. Here, we present single-phase VO2 ultrathin films (thickness less than 20 nm) grown using oxygen plasma molecular beam epitaxy (MBE) on TiO2(001) and Al2O3(0001) substrates. First, we modify existing recipes employing ozone MBE and reproduce the best reported films on TiO2(001); maintaining an almost three order of magnitude transition in a 12 nm thick film. We then extend our recipe to Al2O3(0001) substrates where we stabilize a 12 nm thin single-phase VO2 film and observe a two order of magnitude transition, expanding the possible growth methods for ultrathin VO2 films on Al2O3(0001).In a separate, approximately 10 nm thick VO2 film on TiO2(001), we use noncontact AFM (nc-AFM) to track electronic properties across the expected temperature range of transition. We first observe a change in the work function of VO2 at the expected bulk transition temperature. We then measure the frequency shift and dissipation at varying bias and tip-sample separation at seven stable temperatures, spanning the insulating to the metallic state. Using the frequency shift data, we extract the tip-sample capacitance, then calculate the induced carrier doping within the sample as a result of the proximity of the tip. The work function, carrier density, and damping results above and below the IMT suggest that we observe the IMT; with the damping in particular showing consistent behavior with a decrease in resistance starting as low at 270 K and continuing to 300 K. Furthermore, we observe a change in work function at fixed temperature at close tip-sample separation as low as 240 K, along with elevated damping, suggesting the electric field from the tip itself may be initiating the transition, at least in the surface of the film, at temperatures as low as 240 K in the close tip-sample separation regime. 

Subject Added Entry-Topical Term  

Condensed matter physics.

Subject Added Entry-Topical Term  

Nanoscience.

Subject Added Entry-Topical Term  

Materials science.

Index Term-Uncontrolled  

AFM

Index Term-Uncontrolled  

Frequency shift

Index Term-Uncontrolled  

Phase change

Index Term-Uncontrolled  

Thin film

Index Term-Uncontrolled  

Local doping

Added Entry-Corporate Name  

Harvard University Physics

Host Item Entry  

Dissertations Abstracts International. 84-12B.

Host Item Entry  

Dissertation Abstract International

Electronic Location and Access  

로그인을 한후 보실 수 있는 자료입니다.

소장사항  

202402 2024

Control Number  

joongbu:639597