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Valley-Polarized Charge Transport in Diamond
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Diamond electronics)
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Diamond is a wide bandgap semiconductor with extreme properties such as high thermal conductivity, high breakdown field and high carrier mobilities. These properties together with the possibility to synthesize high purity Single-Crystalline (SC) diamond by Chemical Vapor Deposition (CVD), makes it a really interesting material for electronic devices. The low impurity concentration achieved when fabricating diamonds by CVD allows for a detailed study of the intrinsic electronic properties of diamond, especially at low temperatures when the carrier scattering rate is low.

During the last few years, our group has presented two new phenomena discovered in SC-CVD diamond at temperatures below 150 K. For the very first time, Negative Differential Mobility (NDM) and valley polarization have been observed in diamond. NDM occurs at a temperature range of 110 to 140 K and at an electric field range of 300 to 600 V/cm and has been explained by electron repopulation between different valleys. At temperatures below 100 K, stable valley polarization has been observed due to the low phonon scattering rate in diamond that enable electrons to reside in one valley.

This licentiate thesis will give a short review on electronic properties and charge transport in diamond. It will also present the two discovered phenomena and the methods used to observe them. There will be further discussions of how these discoveries can be used for making future devices, such as the Transferred-Electron Oscillator (TEO) and valleytronic devices.      

Place, publisher, year, edition, pages
Uppsala: Institutionen för teknikvetenskaper , 2015. , 51 p.
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352
Keyword [en]
CVD diamond, valleytronics, Negative Differential Mobility, NDM, electron polarization, Time-of-Flight, ToF, magnetotransport, carrier transport, drift velocity
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-261009OAI: oai:DiVA.org:uu-261009DiVA: diva2:850137
Presentation
(English)
Supervisors
Available from: 2015-09-07 Created: 2015-08-28 Last updated: 2015-09-15Bibliographically approved
List of papers
1. Stability of polarized states for diamond valleytronics
Open this publication in new window or tab >>Stability of polarized states for diamond valleytronics
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2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, no 23, 232105- p.Article in journal (Refereed) Published
Abstract [en]

The stability of valley polarized electron states is crucial for the development of valleytronics. A long relaxation time of the valley polarization is required to enable operations to be performed on the polarized states. Here, we investigate the stability of valley polarized states in diamond, expressed as relaxation time. We have found that the stability of the states can be extremely long when we consider the electron-phonon scattering processes allowed by symmetry considerations. We determine electron-phonon coupling constants by Time-of-Flight measurements and Monte Carlo simulations and use these data to map out the relaxation time temperature dependency. The relaxation time for diamond can be microseconds or longer below 100 K and 100 V/cm due to the strong covalent bond, which is highly encouraging for future use in valleytronic applications. (C) 2014 AIP Publishing LLC.

National Category
Engineering and Technology Physical Sciences
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-229299 (URN)10.1063/1.4882649 (DOI)000337891200043 ()
Available from: 2014-08-06 Created: 2014-08-05 Last updated: 2017-12-05Bibliographically approved
2. Charge Transport Phenomena Unique to Diamond
Open this publication in new window or tab >>Charge Transport Phenomena Unique to Diamond
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2014 (English)In: MRS Online Proceedings Library, Vol. 1591, null-null p.Article in journal (Refereed) Published
Abstract [en]

ABSTRACT Diamond is a unique material in many respects. One of the most well-known extreme properties of diamond is its ultrahardness. This property of diamond actually turns out to have interesting consequences for charge transport, in particular at low temperatures. In fact, the strong covalent bonds that give rise to the ultrahardness results in a lack of short wavelength lattice vibrations which has a strong impact on both electron and hole scattering. In some sense diamond behaves more like a vacuum than other semiconductor materials. In this paper we describe some interesting charge transport properties of diamond and discuss possible novel electronic applications.

Place, publisher, year, edition, pages
Cambridge Journals Online, 2014
Keyword
diamond, electrical properties, electron-phonon interactions
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-237485 (URN)10.1557/opl.2014.295 (DOI)null (ISBN)
Available from: 2014-12-03 Created: 2014-12-03 Last updated: 2015-12-10

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Suntornwipat, Nattakarn

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