Stress dependence of the near-band-gap cathodoluminescence spectrum of GaN determined by spatially resolved indentation method

2006 ◽  
Vol 100 (8) ◽  
pp. 083515 ◽  
Author(s):  
Alessandro Alan Porporati ◽  
Yoshitomo Tanaka ◽  
Atsuo Matsutani ◽  
Wenliang Zhu ◽  
Giuseppe Pezzotti
Keyword(s):  
Band Gap ◽  
Stress Dependence ◽  
Cathodoluminescence Spectrum ◽  
Indentation Method ◽  
Spatially Resolved

Spatially Resolved Photoluminescence in Spontaneously-ordered GaInP2

1999 ◽  
Vol 583 ◽  
Author(s):  
S. Smith ◽  
A. Mascarenhas ◽  
J. M. Olson ◽  
L. L. Kazmerski
Keyword(s):  
Band Gap ◽  
Order Parameter ◽  
Band Gap Energy ◽  
Gap Energy ◽  
Exciton Localization ◽  
Spatially Resolved ◽  
Statistical Variation ◽  
Show Evidence ◽  
Scanning Optical Microscopy ◽  
Comparable Size

AbstractThe low-temperature (5K) photoluminescence (PL) of partially-ordered GaInP2 is spatially resolved using high-resolution (from ˜ 0.2μm-0.7μm) scanning optical microscopy, revealing the spatial variation in band gap energy and the spatial origin of the ordering-induced low-energy emission and the associated ‘quantum-dot-like’ narrow spikes which appear when examining areas smaller, or of comparable size, than a single ordered domain. The large number of spectra taken within a micronsized area allow a detailed look at the statistical variation in band-gap energy and lineshape. A systematic study of a series of samples where the order parameter varies from η ˜ 0 to 0.45 shows that for the most highly-ordered samples, the statisitical distribution of excitonic energy and linewidth show evidence of exciton localization, which is also clearly seen by examining the spatial maps of the excitornic energy and linewidth extracted from the measured spectra.

scholarly journals Optoelectronic Properties of Atomically Thin MoxW(1-x)S2 Nanoflakes Probed by Spatially-Resolved Monochromated EELS

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3218
Author(s):  
Mario Pelaez-Fernandez ◽  
Yung-Chang Lin ◽  
Kazu Suenaga ◽  
Raul Arenal
Keyword(s):  
Band Gap ◽  
2D Materials ◽  
High Energy ◽  
Two Dimensional ◽  
Low Loss ◽  
Huge Amount ◽  
Band Gap Engineering ◽  
Spatially Resolved ◽  
Excitonic Transition ◽  
Electron Energy Loss

Band gap engineering of atomically thin two-dimensional (2D) materials has attracted a huge amount of interest as a key aspect to the application of these materials in nanooptoelectronics and nanophotonics. Low-loss electron energy loss spectroscopy has been employed to perform a direct measurement of the band gap in atomically thin MoxW(1−x)S2 nanoflakes. The results show a bowing effect with the alloying degree, which fits previous studies focused on excitonic transitions. Additional properties regarding the Van Hove singularities in the density of states of these materials, as well as high energy excitonic transition, have been analysed as well.

Biaxial stress dependence of the electrostimulated near-band-gap spectrum of GaN epitaxial film grown on (0001) sapphire substrate

2006 ◽  
Vol 88 (25) ◽  
pp. 251910 ◽  
Author(s):  
Keshu Wan ◽  
Alessandro Alan Porporati ◽  
Gan Feng ◽  
Hui Yang ◽  
Giuseppe Pezzotti
Keyword(s):  
Band Gap ◽  
Sapphire Substrate ◽  
Epitaxial Film ◽  
Biaxial Stress ◽  
Stress Dependence

On the Bandstructure in GaInN/GaN Heterostructures - Strain, Band Gap and Piezoelectric Effect

1998 ◽  
Vol 3 ◽  
Author(s):  
Christian Wetzel ◽  
Shugo Nitta ◽  
Tetsuya Takeuchi ◽  
Shigeo Yamaguchi ◽  
H. Amano ◽  
...  
Keyword(s):  
Band Gap ◽  
Band Gap Energy ◽  
Electronic Band ◽  
Gap Energy ◽  
Spatially Resolved ◽  
Peak Energy ◽  
Electronic Band Gap ◽  
Piezoelectric Field ◽  
New Interpretation ◽  
Piezoelectric Fields

A study of the optoelectronic properties of strained 40 nm Ga1−xInxN layers on GaN films is presented. The fact of pseudomorphic strain leads to a new interpretation of the film composition when derived from x-ray scattering. In addition we directly confirm that strain induces huge piezoelectric fields in this uniaxial system by the observation of Franz-Keldysh oscillations in photoreflection. As a function of composition (0 < x < 0.2) and strain we derive the electronic band gap energy and the piezoelectric field strength. We interpret both in terms of effective bowing parameters and piezoelectric coefficients, respectively. From a spatially resolved micro photoluminescence at room temperature we find no evidence for spatial band gap or composition variations of more than 60 meV over the length scale from 1 to 50 μm (x=0.187) in our material. At the same time, an observed discrepancy between photoluminescence peak energy and photoreflection band gap energy increases with x to some 160 meV. We attribute this redshift to photon assisted tunneling in the huge piezoelectric fields (Franz-Keldysh effect).

Metallic Tin-Filling Effects on Carbon Nanotubes Revealed by Atomically Resolved Spectro-Microscopies

2008 ◽  
Vol 3 ◽  
pp. 1-6 ◽  
Author(s):  
E. Maccallini ◽  
G. Kalantzopoulos ◽  
T. Tsoufis ◽  
R.G. Agostino ◽  
G. Chiarello ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Band Gap ◽  
Local Density ◽  
Electronic States ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Local Density Of States ◽  
Multi Wall Carbon Nanotubes ◽  
Spatially Resolved ◽  
Topology Changes

The identification of features in the Local Density of States (LDOS) of carbon nanotubes (CNTs) obtained by Scanning Tunneling Spectroscopy (STS) is of great importance in order to understand their properties. In this work, Single- and Multi-Wall Carbon Nanotubes are compared with Multi-Wall CNTs filled with tin nanowires (Sn@CNTs) in order to investigate the effect on morphological and electronic properties of the CNTs metallic filling. The LDOS of CNTs, together with topology changes, is investigated by using spatially resolved STM/STS at room temperature and in air and compared to the LDOS of highly oriented pyrolitic graphite (HOPG). The LDOS of CNTs is dominated from different electronic states filling the C 2pσ-2pσ* band gap. The appearance of those states is linked to the diameter and the defects of the CNTs. In fact, Snnanowires encapsulation induces changes in the structure of the CNTs and the appearance of electronic states in the LDOS inside the band gap. A more extensive description of the samples is obtained depicting the morphological features and the vibrational structure on wider areas using Scanning Electron Microscopy (SEM) and Raman spectroscopy, respectively.

Stress dependence of the cathodoluminescence spectrum of N-doped 3C‐SiC

2006 ◽  
Vol 100 (9) ◽  
pp. 093508 ◽  
Author(s):  
Alessandro Alan Porporati ◽  
Koichiro Hosokawa ◽  
Wenliang Zhu ◽  
Giuseppe Pezzotti
Keyword(s):  
Stress Dependence ◽  
Cathodoluminescence Spectrum

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

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