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Improved Optical and Electrical Prop...

Kim, Bumho,

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Improved Optical and Electrical Properties of MoSe2 and WSe2 via Reduction of Point Defects /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Improved Optical and Electrical Properties of MoSe2 and WSe2 via Reduction of Point Defects // Bumho Kim.
Author:	Kim, Bumho,
Description:	1 electronic resource (97 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 82-08, Section: B.
Contained By:	Dissertations Abstracts International82-08B.
Subject:	Nanoscience. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28265029
ISBN:	9798569910397

Improved Optical and Electrical Properties of MoSe2 and WSe2 via Reduction of Point Defects /
Kim, Bumho,

Improved Optical and Electrical Properties of MoSe2 and WSe2 via Reduction of Point Defects /Bumho Kim. - 1 electronic resource (97 pages)

Source: Dissertations Abstracts International, Volume: 82-08, Section: B.

Transition metal dichalcogenides (TMDs) have displayed a host of novel physical phenomena, which opens-up promising future applications in electronics, optoelectronics, spintronics and valleytronics. However, the high defect density of 1012 - 1013 cm-2 in commercially available TMDs may hinder the observation of their intrinsic properties. In this thesis, the defect density of MoSe2 and WSe2 has been reduced by ~10x - 1000x using flux method. The reduced defect denstiy of MoSe2 and WSe2 enables to observe optical and electrical properties approaching their intrinsic properties.First of all, photocurrent measurements on the ultra-clean WSe2 unveil the effect of point defects on photo-response. Substantial improvement of AC photocurrent in the ultra-clean WSe2 indicates that free carriers are likely to non-radiatively decay at atomic defects at room temperature.Then, time-resolved photoluminescence measurements on the ultra-clean MoSe2 samples allow for direct determination of both the intrinsic (radiative) and defect-dependent (non-radiative) lifetimes of trions. In the cleanest MoSe2, the trion quantum yield approaches unity. The long lifetime of 230 ps of trions allows direct observation of their diffusion, conclusively demonstrating that trions are free particles. Both the long radiative and non-radiative lifetime of trions can be attributed to Pauli blocking effects.Morover, transport measurements of ultra-clean WSe2 provide Hall mobility exceeding 10,000 cm2V-1s-1 and long mean free path over 200 nm, which are nearly three times higher than those in previous study. This improved mobility and mean free path in the ultra-clean WSe2 indicate that the electrical properties have been limited by defect scattering.Finally, WSe2 has been a decent platform to generate single photon emitters. However, the microscopic origin of the single photon emitter has been debated. From power- and gate-dependent photoluminescence of ultra-clean WSe2, emerging defect bound excitons are observed, which is likely formed from the interaction between donor defects and excitons.

English

ISBN: 9798569910397Subjects--Topical Terms:

587832
Nanoscience.
Subjects--Index Terms:

Lifetime

Improved Optical and Electrical Properties of MoSe2 and WSe2 via Reduction of Point Defects /
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520 $a Transition metal dichalcogenides (TMDs) have displayed a host of novel physical phenomena, which opens-up promising future applications in electronics, optoelectronics, spintronics and valleytronics. However, the high defect density of 1012 - 1013 cm-2 in commercially available TMDs may hinder the observation of their intrinsic properties. In this thesis, the defect density of MoSe2 and WSe2 has been reduced by ~10x - 1000x using flux method. The reduced defect denstiy of MoSe2 and WSe2 enables to observe optical and electrical properties approaching their intrinsic properties.First of all, photocurrent measurements on the ultra-clean WSe2 unveil the effect of point defects on photo-response. Substantial improvement of AC photocurrent in the ultra-clean WSe2 indicates that free carriers are likely to non-radiatively decay at atomic defects at room temperature.Then, time-resolved photoluminescence measurements on the ultra-clean MoSe2 samples allow for direct determination of both the intrinsic (radiative) and defect-dependent (non-radiative) lifetimes of trions. In the cleanest MoSe2, the trion quantum yield approaches unity. The long lifetime of 230 ps of trions allows direct observation of their diffusion, conclusively demonstrating that trions are free particles. Both the long radiative and non-radiative lifetime of trions can be attributed to Pauli blocking effects.Morover, transport measurements of ultra-clean WSe2 provide Hall mobility exceeding 10,000 cm2V-1s-1 and long mean free path over 200 nm, which are nearly three times higher than those in previous study. This improved mobility and mean free path in the ultra-clean WSe2 indicate that the electrical properties have been limited by defect scattering.Finally, WSe2 has been a decent platform to generate single photon emitters. However, the microscopic origin of the single photon emitter has been debated. From power- and gate-dependent photoluminescence of ultra-clean WSe2, emerging defect bound excitons are observed, which is likely formed from the interaction between donor defects and excitons.
546 $a English
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650 4 $a Nanoscience. $3 587832
650 4 $a Optics. $3 517925
653 $a Lifetime
653 $a Mobility
653 $a Point defect
653 $a Synthesis
653 $a Transition metal dichalcogenide
653 $a Trion
690 $a 0565
690 $a 0752
710 2 $a Columbia University. $b Mechanical Engineering. $e degree granting institution. $3 3815556
720 1 $a Hone, James $e degree supervisor.
720 1 $a Barmak, Katayun $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 82-08B.
790 $a 0054
791 $a Ph.D.
792 $a 2021
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28265029