<link rel="stylesheet" href="styles.cf390c6bfbe7555f.css">

學術出版;;Publications

Permanent URI for this communityhdl:11536/1

收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

Browse

Filters

2006 - 2009132010 - 201932

Settings

🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Cheng, Shun-Jen

Search Results

Now showing 1 - 10 of 45
  • Thumbnail Image
    Item type:Item,
  • Thumbnail Image
    Item type:Item,
    Distinctive Signatures of the Spin- and Momentum-Forbidden Dark Exciton States in the Photoluminescence of Strained WSe2 Monolayers under Thermalization
    (2019-04-01)
    Peng, Guan-Hao
    ;
    Lo, Ping-Yuan
    ;
    Li, Wei-Hua
    ;
    Huang, Yan-Chen
    ;
    Chen, Yan-Hong
    With both spin and valley degrees of freedom, the low-lying excitonic spectra of photoexcited transition-metal dichalcogenide monolayers (TMDC-MLs) are featured by rich fine structures, comprising the intravalley bright exciton states as well as various intra- and intervalley dark ones. The latter states can be classified as those of the spin- and momentum-forbidden dark excitons according to the violated optical selection rules. Because of their optical invisibility, these two types of the dark states are in principle hardly observed and even distinguished in conventional spectroscopies although their impacts on the optical and dynamical properties of TMDC-MLs have been well noticed. In this Letter, we present a theoretical and computational investigation of the exciton fine structures and the temperature-dependent photoluminescence spectra of strained tungsten diselenide monolayers (WSe2-MLs) where the intravalley spin-forbidden dark exciton lies in the lowest exciton states and other momentum-forbidden states are in the higher energies that are tunable by external stress. The numerical computations are carried out by solving the Bethe-Salpeter equation for an exciton in a WSe2-ML under the stress-control in the tight-binding scheme established from the first principle computation in the density functional theory. According to the numerical computation and supportive model analysis, we reveal the distinctive signatures of the spin- and momentum-forbidden exciton states of strained WSe2-MLs in the temperature-dependent photoluminescences and present the guiding principle to infer the relative energetic locations of the two types of dark excitons.
  • Thumbnail Image
    Item type:Item,
    Breakthrough to Non-Vacuum Deposition of Single-Crystal, Ultra-Thin, Homogeneous Nanoparticle Layers: A Better Alternative to Chemical Bath Deposition and Atomic Layer Deposition
    (2017-04-01)
    Liao, Yu-Kuang
    ;
    Liu, Yung-Tsung
    ;
    Hsieh, Dan-Hua
    ;
    Shen, Tien-Lin
    ;
    Hsieh, Ming-Yang
    Most thin-film techniques require a multiple vacuum process, and cannot produce high-coverage continuous thin filmswith the thickness of a fewnanometers on rough surfaces. We present a new "paradigm shift" non-vacuum process to deposit high-quality, ultra-thin, single-crystal layers of coalesced sulfide nanoparticles (NPs) with controllable thickness down to a few nanometers, based on thermal decomposition. This provides high-coverage, homogeneous thickness, and large-area deposition over a rough surface, with little material loss or liquid chemical waste, and deposition rates of 10 nm/min. This technique can potentially replace conventional thin-film deposition methods, such as atomic layer deposition (ALD) and chemical bath deposition (CBD) as used by the Cu(In, Ga) Se2 (CIGS) thin-film solar cell industry for decades. We demonstrate 32% improvement of CIGS thin-film solar cell efficiency in comparison to reference devices prepared by conventional CBD deposition method by depositing the ZnS NPs buffer layer using the new process. The new ZnS NPs layer allows reduction of an intrinsic ZnO layer, which can lead to severe shunt leakage in case of a CBD buffer layer. This leads to a 65% relative efficiency increase.
  • Thumbnail Image
    Item type:Item,
    Electrically sign-reversible transverse g-factors of holes in droplet epitaxial GaAs/AlGaAs quantum dots under uniaxial stress
    (2017-08-23)
    Wu, Yu-Nien
    ;
    Wu, Ming-Fan
    ;
    Ou, Ya-Wen
    ;
    Chou, Ying-Lin
    ;
    Cheng, Shun-Jen
    We present a theoretical investigation of anisotropic g-factor tensors of single holes confined in droplet epitaxial GaAs/AlGaAs quantum dots under electrical and mechanical controls using the gauge-invariant discretization method within the framework of four-band Luttinger-Kohn (k) over right arrow.(p) over right arrow theory. We reveal an intrinsic obstacle to realize the electrical sign reversal of the hole g-factors, being a key condition required for a full spin control in the scheme of g-tensor modulation, for the quantum dots solely with electrical bias control. Constructively, our studies show that, besides electrical gating, slightly stressing an inherently unstrained droplet epitaxial GaAs/AlGaAs quantum dot can offset the transverse hole g-factor to be nearly zero and make the electrical sign reversal of the hole g-factors feasible.
  • Thumbnail Image
    Item type:Item,
    Diamagnetic Response of Exciton Complexes in Semiconductor Quantum Dots
    (2008-12-31)
    Tsai, Ming-Fu
    ;
    Lin, Hsuan
    ;
    Lin, Chia-Hsien
    ;
    Lin, Sheng-Di
    ;
    Wang, Sheng-Yun
    We report measurements of diamagnetic shifts for different exciton complexes confined in small InAs quantum dots. The measured diamagnetic responses are sensitive to the number of carriers in the exciton complexes, with systematic differences between neutral excitons, biexcitons, and trions. Theoretical calculations suggest that such systematic differences arise from very different extents of electron and hole wave functions confined in small quantum dots. The measured magnetic response of Coulomb energies is found to vary with the cube of the wave function extent, and can be a sensitive probe to the electron-hole wave function asymmetry.
  • Thumbnail Image
    Item type:Item,
    Magnetic anisotropy in symmetric magnetic colloidal quantum dots doped with few Mn2+ impurities
    (2009-06-01)
    Cheng, Shun-Jen
    ;
    電子物理學系
    ;
    Department of Electrophysics
    We present numerical exact diagonalization studies of the magnetism in magnetic II-VI colloidal semiconductor quantum dots charged with controlled number of electrons coupled to few magnetic-ion (Mn2+) dopants. The interplay between various relevant spin interactions and the discrete nature of Mn2+ spin distribution is shown to be essential in the magnetism of few Mn2+-doped quantum dots. An interesting revealed feature is the existence of pronounced magnetic anisotropies in symmetric magnetic quantum dots, which are related to the orbital quenchings induced by electron-Mn spin interactions. The orbital quenching effects further lead to significant deviations of the magnetizations of randomly Mn-doped dots from the standard Brillouin-function descriptions.
  • Thumbnail Image
    Item type:Item,
    Spin characteristics of excitonic absorption in multiply charged quantum dots
    (2007-08-01)
    Cheng, Shun-Jen
    ;
    電子物理學系
    ;
    Department of Electrophysics
    The excitonic absorption spectra of negatively charged self-assembled quantum dots as a function of resident electron number (N-e=0-5) are theoretically studied using the configuration interaction method. Spin Pauli blockade, Coulomb (exchange and correlation) interactions, and symmetry of dot shape are identified as the three main underlying mechanisms, sensitively depending on N-e, in the spin characteristic spectra. In particular, we predict that polarized absorption in triply charged dots exhibits anomalous spin-dependent features, resulting from the intrinsic correlations in charged exciton X-3.
  • Thumbnail Image
    Item type:Item,
    Theory of magnetism in diluted magnetic semiconductor nanocrystals
    (2008-03-01)
    Cheng, Shun-Jen
    ;
    電子物理學系
    ;
    Department of Electrophysics
    We present a theoretical investigation of magnetism in II-VI diluted magnetic semiconductor nanocrystals (NCs). The energy spectra, magnetizations, and magnetic susceptibilities of singly charged NCs with few substitutional magnetic Mn2+ ions are studied as functions of NC size, magnetic dopant distribution, and concentration by using the technique of exact diagonalization. For NCs containing long range interacting Mn ions, the quantum size effects improve the stability of ferromagnetic magnetic polarons. The carrier-mediated spin interactions between magnetic ions result in the enhancement of magnetism. By contrast, the ground states of NCs containing short ranged Mn clusters undergo a series of magnetic phase transitions from antiferromagnetism to ferromagnetism, with decreasing size of NC. An analysis based on a simplified constant interaction model, supported by the numerical calculations of local mean field theory, is presented for the magnetic NCs with many magnetic ions over a wide range of Mn concentration and NC size. Accordingly, we derive the condition for the formation of magnetic polaron and predict the observable signatures of the magnetic phases in magnetization measurements.
  • Thumbnail Image
    Item type:Item,
    Nonresonant carrier transfer in single InGaAs/GaAs quantum dot molecules
    (2008-06-01)
    Chang, Wen-Hao
    ;
    Lin, Hsuan
    ;
    Wang, Sheng-Yun
    ;
    Lin, Chia-Hsien
    ;
    Cheng, Shun-Jen
    We present a spectroscopic study of single quantum dot molecules (QDMs) formed by two closely stacked In(0.5)Ga(0.5)As layers. The exciton fine structures as well as direct and indirect excitonic species associated with QDMs were identified by power dependent and polarization resolved microphotoluminescence measurements. As the temperature was increased, a directional energy transfer between the direct and indirect excitons in single QDMs was observed. A rate-equation model was developed to explain our data. We show that a phonon-assisted nonresonant tunneling of the hole between the two adjacent dots is responsible for such directional energy transfers in QDMs.
  • Thumbnail Image
    Item type:Item,
    Anticorrelation between the splitting and polarization of the exciton fine structure in single self-assembled InAs/GaAs quantum dots
    (2011-02-28)
    Lin, Chia-Hsien
    ;
    You, Wen-Ting
    ;
    Chou, Hsiang-Yu
    ;
    Cheng, Shun-Jen
    ;
    Lin, Sheng-Di
    We report on a systematic correlation between the fine-structure splitting and polarization anisotropy of excitons in InAs/GaAs quantum dots, but with an unexpected reversal in order of the polarization eigenaxes. Such an anticorrelation is explained by a large valence-band-mixing induced splitting due to the shape and strain anisotropies. The strength and phase of valence band mixing are also found to play an important role in the tuning of fine structure splitting using an in-plane magnetic field.