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Using Non-Contact AFM to Study the Local Doping and Damping Through the Transition in an Ultrathin VO2 Film.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Using Non-Contact AFM to Study the Local Doping and Damping Through the Transition in an Ultrathin VO2 Film./
Author:	Spitzig, Alyson.
Description:	1 online resource (136 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
Subject:	Condensed matter physics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30491822click for full text (PQDT)
ISBN:	9798379613389

Using Non-Contact AFM to Study the Local Doping and Damping Through the Transition in an Ultrathin VO2 Film.
Spitzig, Alyson.

Using Non-Contact AFM to Study the Local Doping and Damping Through the Transition in an Ultrathin VO2 Film. - 1 online resource (136 pages)

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

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

Includes bibliographical references

Bulk 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.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798379613389Subjects--Topical Terms:

3173567
Condensed matter physics.
Subjects--Index Terms:

AFMIndex Terms--Genre/Form:

542853
Electronic books.

Using Non-Contact AFM to Study the Local Doping and Damping Through the Transition in an Ultrathin VO2 Film.
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520 $a Bulk 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.
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653 $a Local doping
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