Observation of Redshifts of Photoluminescence from Thin Films Assembled by CuCl Nanoclusters

1997 ◽  
Vol 11 (06) ◽  
pp. 275-281
Author(s):  
Bingyou Miao ◽  
Jianmin Hong ◽  
Pingping Chen ◽  
Xiaoli Yuan ◽  
Min Han ◽  
...  
Keyword(s):  
Thin Films ◽  
Quantum Confinement ◽  
Phonon Coupling ◽  
Transmission Electron ◽  
Two Samples ◽  
Evaporation Technique ◽  
The Mean ◽  
Quartz Substrates ◽  
Cucl Nanocrystals ◽  
Gas Evaporation Technique

Two samples of thin films, assembled by CuCl nanoclusters, have been prepared by the gas evaporation technique. The CuCl nanoclusters were deposited on monocrystalline silicon and quartz substrates and then coated with a layer of NaCl to prevent oxidation of the CuCl nanoclusters. From transmission electron microscope and selected area diffraction, it is clear that the two samples consist of CuCl nanocrystals and Cu aggregates and the mean diameters are about 3 nm and 6 nm. From the absorption and photoluminescence (PL) spectra of the two samples carried out at ~300 K, we found that the peaks of exciton absorption do not show up and luminescence peaks shift to lower energies, possibly due to the strong coupling between exciton and phonon. At 77 K, the PL peaks of excitons broadened by exciton–phonon coupling have been observed, in approximate agreement with the values calculated by the quantum confinement model. The broad peaks of emission from trapped states or bands have also been observed at 77 K. In addition, the interaction between exciton and phonon is stronger in the sample with mean diameter about 3 nm according to a larger broadening and redshift of the PL peak from excitons, in qualitative agreement with theoretical prediction.

Growth of BaTiO3 Thin Films by MOCVD

1993 ◽  
Vol 335 ◽  
Author(s):  
Debra L. Kaiser ◽  
Mark D. Vaudin ◽  
Greg Gillen ◽  
Cheol-Seong Hwang ◽  
Lawrence H. Robins ◽  
...  
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Chemical Vapor ◽  
Titanium Isopropoxide ◽  
Elevated Pressure ◽  
Process Gas ◽  
Polycrystalline Thin Films ◽  
Transmission Electron ◽  
Quartz Substrates ◽  
Secondary Ion

AbstractPolycrystalline thin films of BaTiO3 were deposited on fused quartz substrates at 600°C by metalorganic chemical vapor deposition (MOCVD). The films were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), secondary ion mass spectroscopy (SIMS) and Raman spectroscopy. Films prepared in the early stages of this study that had appeared to contain only crystalline BaTiO3 by XRD were found to have nonuniform composition and microstructure through the film thickness by SIMS and TEM. The MOCVD system was then modified by installing a process gas bypass apparatus and an elevated pressure bubbler for the titanium isopropoxide precursor. A 1.2 μm thick BaTiO3 film prepared in the modified system demonstrated much improved compositional and microstructural uniformity through the thickness of the film. This film had a columnar microstructure with grain widths of 0.1–0.2 μm and exhibited tetragonality as detected by Raman spectroscopy.

scholarly journals Structural and Optical Properties of Nanocrystalline 3,4,9,10-Perylene-Tetracarboxylic-Diimide Thin Film

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
M. M. El-Nahhas ◽  
H. Abdel-Khalek ◽  
E. Salem
Keyword(s):  
Optical Properties ◽  
Film Thickness ◽  
Normal Incidence ◽  
Band Model ◽  
X Ray Diffraction ◽  
Dispersion Energy ◽  
Transmission Electron ◽  
Indirect Allowed Transition ◽  
Evaporation Technique ◽  
Quartz Substrates

Thin films of nanocrystalline 3,4,9,10-perylene-tetracarboxylic-diimide (PTCDI) were prepared on quartz substrates by thermal evaporation technique. The structural properties were identified by transmission electron microscopy (TEM) and the X-ray diffraction (XRD). The optical properties for the films were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500 nm. The optical constants (refractive indexnand absorption indexk) were calculated and found to be independent on the film thickness in the measured film thickness range 117–163 nm. The dispersion energy (Ed), the oscillator energy (Eo), and the high-frequency dielectric constantε∞were obtained. The energy band model was applied, and the types of the optical transitions responsible for optical absorption were found to be indirect allowed transition. The onset and optical energy gaps were calculated, and the obtained results were also discussed.

Activation Volume for Inelastic Deformation in Polycrystalline Ag Films at Low Temperatures

1999 ◽  
Vol 594 ◽  
Author(s):  
Mauro J. Kobrinsky ◽  
Carl V. Thompson
Keyword(s):  
Thin Films ◽  
Inelastic Deformation ◽  
Activation Volume ◽  
Metallic Thin Films ◽  
Thermally Activated ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Relaxation Experiments ◽  
The Mean

AbstractThe low temperature (T < 100 °C) inelasticity of polycrystalline Ag thin films on thick substrates has been studied. In-situ Transmission Electron Microscopy and stress-relaxation experiments indicate that thermally-activated glide of dislocations through forest-dislocation obstacles is the dominant inelastic mechanism. Values of the activation volume for inelastic deformation obtained with both experiments are reported. The mean distance between obstacles along the length of moving dislocations was found to be significantly smaller than the thickness of the film and the average grain size, which explains why current models for dislocationmediated plasticity underestimate the strength of thin films. Results from these experiments on Ag are expected to be representative of other metallic thin films (e.g. Cu and Au) on substrates.

Atomic Observation of the Sublimation Process of the Pb (111) Surface

2003 ◽  
Vol 10 (02n03) ◽  
pp. 455-459 ◽  
Author(s):  
T. Tanigaki ◽  
H. Suzuki ◽  
Y. Kimura ◽  
C. Kaito ◽  
Y. Saito
Keyword(s):  
Electron Microscope ◽  
Video Recording ◽  
Carbon Film ◽  
Atomic Layer ◽  
Carbon Layer ◽  
Sublimation Process ◽  
Step Flow ◽  
Transmission Electron ◽  
Evaporation Technique ◽  
Gas Evaporation Technique

The dynamic behavior of the sublimation process using ultrafine Pb particles produced by the gas evaporation technique was examined at the level of atomic resolution using a transmission electron microscope equipped with a real-time video-recording system. The ultrafine Pb particles coated with a carbon layer with a thickness of the order of 5 nm were prepared in the electron microscope by heating particles on carbon film at 300°C. Sublimation of the Pb particle covered with the carbon layer took place above 470°C, which is slightly higher than the melting point of Pb. Sublimation occurred at the surface with a higher surface energy. The sublimation process of the (111) surface was clearly observed at an atomic level. It was found that two- or four-atomic-layer step flow was observed at the (111) surface. At the (111) surface between the stacking faults, two-layer and successive one-layer sublimation occurred.

High-resolution observations of PbS adsorbed structures on Mg (00.1) surface

1983 ◽  
Vol 41 ◽  
pp. 294-295
Author(s):  
N. Tanaka ◽  
K. Mihama
Keyword(s):  
Carbon Films ◽  
Surface Structures ◽  
Atomic Resolution ◽  
Specimen Preparation ◽  
Characteristic Surface ◽  
Present Specimen ◽  
Transmission Electron ◽  
Evaporation Technique ◽  
Reflection Electron Diffraction ◽  
Gas Evaporation Technique

Characteristic surface structures and adsorbed structures of metals and semiconductors have been elucidated by reflection electron diffraction techniques such as LEED and RHEED. These techniques, however, can not give the information about the atomic arrangements or adsorbed sites in a direct way. The present work is the first trial of observing the adsorbed structures of PbS grown on Mg (00.1) surfaces with atomic resolution by using transmission electron microscopy. For such trials, the specimen preparation is the most important problem which decides the success of the observations. Especially, clean, flat and thin (∽10nm) substrates should be prepared.The present specimen substrates are Mg‐platelike particles prepared by gas evaporation technique. The procedure of the specimen preparation is as follows: Mg-platelike particles (thickness ∽ 20nm) are prepared by the evaporation of Mg ribbon in 10 Torr of argon and gathered on a perforated carbon films. After re-evacuation down to 1 × 10-8 Torr of the chamber, PbS of less than 1 nm in mean thickness is deposited on the Mg-plates.

A standard for transmission electron spectroscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 530-531 ◽  
Author(s):  
Dennis Maher ◽  
David Joy ◽  
Peggy Mochel
Keyword(s):  
Thin Films ◽  
Electron Spectroscopy ◽  
Host Lattice ◽  
Single Element ◽  
Multicomponent Systems ◽  
Transmission Electron ◽  
Major Interest ◽  
Standard Specimens ◽  
Forms Of Carbon ◽  
Electron Energy Loss

A variety of standard specimens is needed in order to systematically investigate the instrumentation, specimen, data reduction and quantitation variables in electron energy-loss spectroscopy (EELS). Pure single element specimens (e.g. various forms of carbon) have received considerable attention to date but certain elements of interest cannot be prepared directly as thin films. Since studies of the first and second row elements in two- or multicomponent systems will be of considerable importance in microanalysis using EELS, there is a need for convenient standards containing these species. For many investigations a standard should contain the desired element, or elements, homogeneously dispersed through a suitable matrix and at an accurately known concentration. These conditions may be met by the technique of implantation.Silicon was chosen as the host lattice since its principal ionization energies, EL23 = 98 eV and Ek = 1843 eV, are well removed from the K-edges of most elements of major interest such as boron (Ek = 188 eV), carbon (Ek = 283 eV), nitrogen (Ek = 400 eV) and oxygen (Ek = 532 eV).

Transmission Electron Microscopy studies of the vacancy ordering in YSI2-X thin films

1991 ◽  
Vol 49 ◽  
pp. 562-563
Author(s):  
F.-R. Chen ◽  
T. L. Lee ◽  
L. J. Chen
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Thin Films ◽  
Diffraction Pattern ◽  
Annealing Temperature ◽  
Lattice Mismatch ◽  
Si Substrate ◽  
Metal Thin Films ◽  
Transmission Electron ◽  
Vacancy Ordering

YSi2-x thin films were grown by depositing the yttrium metal thin films on (111)Si substrate followed by a rapid thermal annealing (RTA) at 450 to 1100°C. The x value of the YSi2-x films ranges from 0 to 0.3. The (0001) plane of the YSi2-x films have an ideal zero lattice mismatch relative to (111)Si surface lattice. The YSi2 has the hexagonal AlB2 crystal structure. The orientation relationship with Si was determined from the diffraction pattern shown in figure 1(a) to be and . The diffraction pattern in figure 1(a) was taken from a specimen annealed at 500°C for 15 second. As the annealing temperature was increased to 600°C, superlattice diffraction spots appear at position as seen in figure 1(b) which may be due to vacancy ordering in the YSi2-x films. The ordered vacancies in YSi2-x form a mesh in Si plane suggested by a LEED experiment.

Transmission Electron Microscopy studies of texture of Cr underlayer of magnetic recording hard disk

1991 ◽  
Vol 49 ◽  
pp. 580-581
Author(s):  
L. Tang ◽  
G. Thomas ◽  
M. R. Khan ◽  
S. L. Duan
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Magnetic Recording ◽  
Magnetic Thin Films ◽  
Magnetic Films ◽  
Substrate Bias ◽  
Epitaxial Relationship ◽  
Transmission Electron

Cr thin films are often used as underlayers for Co alloy magnetic thin films, such as Co1, CoNi2, and CoNiCr3, for high density longitudinal magnetic recording. It is belived that the role of the Cr underlayer is to control the growth and texture of the Co alloy magnetic thin films, and, then, to increase the in plane coercivity of the films. Although many epitaxial relationship between the Cr underlayer and the magnetic films, such as ﹛1010﹜Co/ {110﹜Cr4, ﹛2110﹜Co/ ﹛001﹜Cr5, ﹛0002﹜Co/﹛110﹜Cr6, have been suggested and appear to be related to the Cr thickness, the texture of the Cr underlayer itself is still not understood very well. In this study, the texture of a 2000 Å thick Cr underlayer on Nip/Al substrate for thin films of (Co75Ni25)1-xTix dc-sputtered with - 200 V substrate bias is investigated by electron microscopy.

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