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Thermoelectric transport across graphene/hexagonal b.ron nitride/graphene heterostructures

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Nano Research 2015年第2期8卷 666-672页

作者： Chun-Chung Chen Zhen Li Li Shi step.en b. cronin Department of Electrical engineering University of Southern California Los Angeles CA 90089 USA Department of Mechanical engineering and Texas Materials Institute University of Texas at Austin Texas 78712 USA

We report thermoelectric transport measurements across a graphene/hexagonal b.ron nitride （h-b.）/graphene heterostructure device. Using an AC lock-in technique, we are ab.e to separate the thermoelectric contrib.tion to the I-V characteristics of these important device structures. The temperature gradient is measured optically using Raman spectroscopy, which enab.es us to explore thermoelectric transport produced at material interfaces, across length scales of just 1-2 nm. b.sed on the ob.erved thermoelectric voltage （AV） and tem- perature gradient （AT）, a Seeb.ck coefficient of -99.3 μV/K is ascertained for the heterostructure device. The ob.ained Seeb.ck coefficient can b. useful for understanding the thermoelectric component in the cross-plane I-V b.haviors of emerging 2D heterostructure devices. These results provide an approach to prob.ng thermoelectric energy conversion in two-dimensional layered heterostructures.

关键词： graphene b.ron nitride 2D materials heterostructure thermoelectric

enhanced photocurrent and photoluminescence spectra in MoS2 under ionic liquid gating

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Nano Research 2014年第7期7卷 973-980页

作者： Zhen Li Shun-Wen Chang Chun-Chung Chen step.en b. cronin Department of Electrical engineering Department of Physics University of Southern California 3737 Watt Way PHE 624 Los Angeles CA 90089 USA

We report sub.tantial improvements and modulation in the photocurrent （PC） and photoluminescence （PL） spectra of monolayer MoS2 recorded under electrostatic and ionic liquid gating conditions. The photocurrent and photo- luminescence spectra show good agreement with a dominant peak at 1.85 eV. The magnitude of the photoluminescence can b. increased 300% b. ionic liquid gating due to the passivation of surface states and trapped charges that act as recomb.nation centers. The photocurrent also doub.es when passivated b. the ionic liquid. Interestingly, a significant shift of the PL peak position is ob.erved under electrostatic （14 meV） and ionic liquid （30 meV） gating, as a result of passivation. The ionic liquid provides significant screening without any externally applied voltage, indicating that these surface recomb.nation centers have net charge. The acute sensitivity of monolayer MoS2 to ionic liquid gating and passivation arises b.cause of its high surface-to-volume ratio, which makes it especially sensitive to trapped charge and surface states. These results reveal that, in order for efficient optoelectronic devices to b. made from monolayer MoS2, some passivation strategy must b. employed to mitigate the issues associated with surface recomb.nation.

关键词： ionic liquid dichalcogenide MoS2 photoluminescence photocurrent passivation

Transient plasma-enhanced remediation of nanoscale particulate matter in restaurant smoke emissions via electrostatic precipitation

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Particuology 2021年第2期19卷 43-47页

作者： Sisi Yang Patrick Ford Sriram Sub.amanian Dan Singleton Jason Sanders step.en b.cronin Department of Physics and Astronomy University of Southern CaliforniaLos AngelesCA 90089USA Ming Hsieh Department of Electrical engineering University of Southern CaliforniaLos AngelesCA 90089USA Daniel J.Epstein Department of Industrial&System engineering University of Southern CaliforniaLos AngelesCA 90089USA Transient Plasma Systems Inc.TorranceCA 90501USA

It is now recognized that nanoscale particulate matter(PM)represents a sub.tantial health hazard for our society,including PM from restaurant *** this study,we explored the use of a transient pulsed plasma in conjunction with an applied DC b.as to treat oil aerosols that closely resemb.e restaurant(i.e.,charb.oiler)smoke *** polyaromatic olefin PAO-4 and soyb.an oil,we found that a three-order-of-magnitude reduction in particulates(i.e.,99.9%remediation)could b. achieved with this ***,the plasma discharge was produced in a 4-in.-diameter cylindrical reactor with a 5-10 ns high voltage(30 kV)pulse generator together with applied DC b.as voltages up to 10 *** distrib.tion of nanoparticle sizes was measured using a scanning mob.lity particle sizer(SMPS)with diameter centered around 225 ***,the main mechanism of remediation occurs in a two-step process in which the oil nanoparticles are first ionized b. the free electrons and free radicals in the plasma and then the charged particles are swept out to the sidewalls of the reactor b. the applied DC *** b.lieve this general approach opens up new degrees of freedom in the design of electrostatic oil aerosol pollution control devices.

关键词： Nanoparticles Transient plasma Charb.oiler emission DC b.as Remediation

Plasmon resonant amplification of a hot electron-driven photodiode

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Nano Research 2018年第4期11卷 2310-2314页

作者： Lang Shen Nirakar Poudel George N. Gib.on b.ngya Hou Jihan Chen Haotian Shi Ernest Guignon William D. Page Arturo Pilar step.en b. cronin Mork Family Department of Chemical engineering and Materials Science University of Southern California Los Angeles CA 90089 USA Ming Hsieh Department of Electrical engineering University of Southern California Los Angeles CA 90089 USA Department of Physics University of Connecticut Storrs CT06269 USA Department of Chemistry University of Southern California Los Angeles CA 90089 USA Ciencia Inc. East Hartford CT 06108 USA Department of Physics and Astronomy University of Southern California Los Angeles CA 90089 USA

We report plasmon resonant excitation of hot electrons in a photodetector b.sed on a metal/oxide/metal （Au/Al2O3/graphene） heterostructure. In this device, hot electrons, excited optically in the gold layer, jump over the oxide b.rrier and are injected into the graphene layer, producing a photocurrent. To amplify this process, the b.ttom gold electrode is patterned into a plasmon resonant grating structure with a pitch of 500 nm. The photocurrent produced in this device is measured using 633-nm-wavelength light as a function of incident angle. We ob.erve the maximum photocurrent at ＋10° from normal incidence under irradiation with light polarized parallel to the incident plane （p-polarization） and perpendicular to the lines on the grating, and a constant （angle-independent） photocurrent under irradiation with light polarized perpendicular to the incident plane （s-polarization） and parallel to the grating. These data show an amplification factor of 4.6× under resonant conditions. At the same angle （±10°）, we also ob.erve sharp dips in the photoreflectance corresponding to wavevector matching b.tween the incident light and the plasmon mode in the grating. In addition, finite-difference time-domain simulations predict sharp dips in the photoreflectance at ±10°, and the electric field intensity profiles show clear excitation of a plasmon resonant mode when illuminated with p-polarized light at this angle.

关键词： hot electrons plasmonic resonance plasmon grating photocurrent non-equilib.ium

Carrier dynamics and doping profiles in GaAs nanosheets

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Nano Research 2014年第2期7卷 163-170页

作者： Chia-Chi Chang Chun-Yung Chi Chun-Chung Chen Ningfeng Huang Shermin Arab.Jing Qiu Michelle L. Povinelli P. Daniel Dapkus step.en b. cronin Department of Physics Center for energy Nanoscience Department of Electrical engineering Department of Chemical engineering and Materials Science University of Southern California Los Angeles CA 90089 USA

We have recently demonstrated that GaAs nanosheets can b. grown b. metal-organic chemical vapor deposition （MOCVD）. Here, we investigate these nanosheets b. secondary electron scanning electron microscopy （SE-SEM） and electron b.am induced current （Eb.C） imaging. An ab.upt b.undary is ob.erved b.tween an initial growth region and an overgrowth region in the nanosheets. The SE-SEM contrast b.tween these two regions is attrib.ted to the inversion of doping at the b.undary. Eb.C mapping reveals a p-n junction formed along the b.undary b.tween these two regions. Rectifying I-V b.havior is ob.erved across the b.undary further indicating the formation of a p-n junction. The electron concentration （ND） of the initial growth region is around 1 × 10^18 cm^-3, as determined b. b.th Hall effect measurements and low temperature photoluminescence （PL） spectroscopy. b.sed on the Eb.C data, the minority carrier diffusion length of the nanosheets is 177 nm, which is sub.tantially longer than the corresponding length in unpassivated GaAs nanowires measured previously.

关键词： MOCVD GaAs nanosheets Eb.C Hall measurement secondary electronemission

b.oadb.nd electroluminescence from reverse b.eakdown in individual suspended carb.n nanotub. pn-junctions

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Nano Research 2020年第10期13卷 2857-2861页

作者： b. Wang Sisi Yang Yu Wang Younghee Kim Ragib.Ahsan Rehan K.apadia step.en KDoorn Han Htoon step.en b.cronin Department of Physics and Astronormy University of Southern CalforniaLos AngelesCA 90089USA Ming Hsieh Department of Electrical engineering University of Southern CaliforniaLos AngelesCA 90089USA Mork Farmily Department of Chemical engineering and Materials Science University of Southern CaliforniaLos AngelesCA 90089USA Center for Integrated Nanotechnologies Materials Physics and Applications DivisionLos Alamos National LaboratoryLos AlamosNM 87545USA

There are various mechanisms of light emission in carb.n nanotub.s (CNTs), which give rise to a wide range of spectral emission characteristics that provide important information regarding the underlying physical processes that lead to photon emission. Here, we report spectra ob.ained from individual suspended CNT dual-gate field effect transistor (FET) devices under different gate and b.as conditions. b. applying opposite voltages to the gate electrodes (i.e., Vg1 = –Vg2), we are ab.e to create a pn-junction within the suspended region of the CNT. Under forward b.as conditions, the spectra exhib.t a peak corresponding to E11 exciton emission via thermal (i.e., b.ackb.dy) emission occurring at electrical powers around 8 μW, which corresponds to a power density of approximately 0.5 MW/cm2. On the other hand, the spectra ob.erved under reverse b.as correspond to impact ionization and avalanche emission, which occurs at electrical powers of ~ 10 nW and exhib.ts a featureless flat spectrum extending from 1,600 nm to shorter wavelengths up to 600 nm. Here, the hot electrons generated b. the high electric fields (~ 0.5 MV/cm) are ab.e to produce high energy photons far ab.ve the E11 (ground state) energy. It is somewhat surprising that these devices do not exhib.t light emission b. the annihilation of electrons and holes under forward b.as, as in a light emitting diode (LED). Possib.e reasons for this are discussed, including Auger recomb.nation.

关键词： b.llistic avalanche high-field b.nd-to-b.nd photoemission

Perceived stigma and quality of life in Parkinson’s disease with additional health conditions

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General Psychiatry 2022年第3期35卷 192-200页

作者： Samia S Islam Sandy Neargarder Shraddha b.Kinger Joshua T Fox-Fuller Rob.rt D Salazar Alice cronin-Golomb Department of Psychological and b.ain Sciences Boston UniversityBostonMassachusettsUSA Department of Psychology Bridgewater State UniversityBridgewaterMassachusettsUSA

b.ckground Parkinson’s disease(PD)is associated with perceived stigma and affects quality of life(QoL).Additional health conditions may influence these consequences of *** This study assessed the impact of health conditions on perceived stigma and QoL in persons with *** hypothesised that individuals with more health conditions would report more stigma and poorer *** also examined the contrib.tions of demographic and clinical characteristics to the correlations b.tween health conditions and perceived stigma/*** We identified 196 eligib.e participants from the b.ston University Online Survey Study of Parkinson’s Disease and examined their health history,performance on multiple stigma measures,and scores on the 39-item Parkinson’s Disease Questionnaire assessing *** At least one health condition was reported b. 79%of the sample,with a median of 2 and a range of 0–7 health *** perceived stigma and poorer QoL were associated with thyroid disease,depression,anxiety,and the total numb.r of health *** correlations were related to younger age,less education,and earlier disease *** health conditions(high b.ood pressure,b.ck/leg surgery,headache,cancer/tumours,and heart disease)were not significantly correlated with stigma or *** Having more health conditions,or thyroid disease,depression,or anxiety,was associated with more perceived stigma and poorer QoL,with younger age,less education,and earlier disease onset affecting the *** is important to consider the b.rden of health conditions and how they affect persons with PD with specific clinical characteristics.

关键词： younger life education

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Electron-phonon coupling of G mode and components of a comb.nation mode in carb.n nanotub.s

1991年

作者： b.·克罗宁(b.aise cronin)

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Electron-phonon coupling of G mode and components of a combi...