Comparative Study of Emission from Highly Excited (In, Al) GaN Thin Films and Heterostructures

1999 ◽  
Vol 572 ◽  
Author(s):  
B. D. Little ◽  
S. Bidnyk ◽  
T. J. Schmidt ◽  
J. B. Lam ◽  
Y. H. Kwon ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Room Temperature ◽  
Laser Diodes ◽  
Stimulated Emission ◽  
Optically Pumped ◽  
Al Content ◽  
Order Of Magnitude ◽  
Deep Ultraviolet ◽  
Optical Waveguiding

ABSTRACTThe optical properties of (In, Al) GaN thin films and heterostructures have been compared under the conditions of strong nanosecond excitation. The stimulated emission (SE) threshold from AIGaN epilayers was found to increase with increasing Al content compared to GaN, in contrast to InGaN epilayers, where an order of magnitude decrease is observed. Optically pumped SE has been observed from AIGaN films with aluminum concentrations as high as 26%. Room temperature SE at wavelengths as low as 327 nm has been achieved. In contrast to the increase of SE threshold seen for AlGaN films, we found that AlGaN/GaN heterostructures which utilize carrier confinement and optical waveguiding drastically enhance the lasing characteristics. We demonstrate that AIGaN/GaN heterostructures are suitable for the development of deep ultraviolet laser diodes.

Molecular Beam Epitaxy of Znl-x Cdx Se/ZnSe Heterostructures And Their Optical Properties

1991 ◽  
Vol 228 ◽  
Author(s):  
H. Luo ◽  
N. Samarth ◽  
J. K. Furdyna ◽  
H. Jeon ◽  
J. Ding ◽  
...  
Keyword(s):  
Optical Properties ◽  
Molecular Beam Epitaxy ◽  
Quantum Wells ◽  
Room Temperature ◽  
Molecular Beam ◽  
Stimulated Emission ◽  
Optically Pumped ◽  
Absorption Coefficients ◽  
Excitonic Absorption ◽  
Lasing Mechanism

ABSTRACTSuperlattices and quantum wells of Znl-xCdxSe/ZnSe, and heterostructures based on ZnSe/CdSe digital alloys have been grown by molecular beam epitaxy (MBE). Their optical properties were studied with particular emphasis on excitonic absorption and photopumped stimulated emission. Excitonic absorption is easily observable up to 400 K, and is characterized by extremely large absorption coefficients (α = 2×105cm−1). Optically pumped lasing action is obtained at room temperature with a typical threshold intensity of 100 kW/cm2. The lasing mechanism in these II-VI quantum wells appears to be quite different from that in the better studied III-V materials: in our case, the onset of stimulated emission occurs before the saturation of the excitonic absorption, and the stimulated emission occurs at an energy lower than that of the excitonic absorption.

Room-temperature deep-ultraviolet-stimulated emission from AlxGa1−xN thin films grown on sapphire

1999 ◽  
Vol 74 (2) ◽  
pp. 245-247 ◽  
Author(s):  
T. J. Schmidt ◽  
Yong-Hoon Cho ◽  
J. J. Song ◽  
Wei Yang
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Stimulated Emission ◽  
Deep Ultraviolet

Structure and Conductivity of Iodine-Doped C60 Thin Films

1994 ◽  
Vol 359 ◽  
Author(s):  
Jun Chen ◽  
Haiyan Zhang ◽  
Baoqiong Chen ◽  
Shaoqi Peng ◽  
Ning Ke ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Room Temperature ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
X Ray ◽  
Thermally Activated ◽  
Order Of Magnitude

ABSTRACTWe report here the results of our study on the properties of iodine-doped C60 thin films by IR and optical absorption, X-ray diffraction, and electrical conductivity measurements. The results show that there is no apparent structural change in the iodine-doped samples at room temperature in comparison with that of the undoped films. However, in the electrical conductivity measurements, an increase of more that one order of magnitude in the room temperature conductivity has been observed in the iodine-doped samples. In addition, while the conductivity of the undoped films shows thermally activated temperature dependence, the conductivity of the iodine-doped films was found to be constant over a fairly wide temperature range (from 20°C to 70°C) exhibiting a metallic feature.

Microstructure and Optical Properties of Co Sputter Deposited Si-Al Nanocomposite Thin Films

2000 ◽  
Vol 648 ◽  
Author(s):  
F. Niu ◽  
P.J. Dobson ◽  
B. Cantor
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Optical Absorption ◽  
Absorption Peak ◽  
Al Content ◽  
Al Nanoparticles ◽  
Transmission Electron ◽  
Effective Medium Theories ◽  
Nanocomposite Thin Films ◽  
Sputter Deposited

AbstractNovel Si-Al nanocomposite thin films were made by radio frequency co-sputtering of Si and Al with Al content from 0 at.% to 69 at.%. Microstructure and optical properties of the films were characterised by conventional and high resolution transmission electron microscopyand spectrometry in the wavelength range from 200 to 3000 nm. The film microstructure consisted of Al nanoparticles (2-9 nm) embedded in an amorphous Si-Al matrix. Optical absorption spectra of the films up to 50 at.% Al exhibited a sharp absorption peak below500 nm and relatively low absorption above 500 nm. In addition, the absorption peak shifted towards longer wavelengths and the general absorption above 500 nm increased remarkably as Al content increased. For the Si-69at.%Al films, however, an absorption plateau appeared between 300 nm to 700 nm and a second weak and broad absorption peak appeared at around 900 nm. The results are analysed and compared with the optical absorption predicted by various effective medium theories.

scholarly journals Optical and magneto-optical properties of GdxFe(100-x) thin films close to the compensation point

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Eva Jesenská ◽  
Takayuki Ishibashi ◽  
Lukáš Beran ◽  
Martin Pavelka ◽  
Jaroslav Hamrle ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Spectral Dependence ◽  
Room Temperature ◽  
Magnetic Moments ◽  
Perpendicular Magnetic Anisotropy ◽  
Theoretical Models ◽  
Compensation Point ◽  
Spin Torque ◽  
Dc Sputtering

Abstract Unlike ferromagnetic materials, ferrimagnetic metals have recently received considerable attention due to their bulk perpendicular magnetic anisotropy, low net magnetization and tunable magnetic properties. This makes them perfect candidates for the research of recently discovered spin-torque related phenomena. Among other ferrimagnetic metals, GdFe has an advantage in relatively large magnetic moments in both sublattices and tunability of compensation point above the room temperature by small changes in its composition. We present a systematic study of optical and magneto-optical properties of amorphous GdxFe(100-x) thin films of various compositions (x = 18.3, 20.0, 24.7, 26.7) prepared by DC sputtering on thermally oxidized SiO2 substrates. A combination of spectroscopic ellipsometry and magneto-optical spectroscopy in the photon energy range from 1.5 to 5.5 eV with advanced theoretical models allowed us to deduce the spectral dependence of complete permittivity tensors across the compensation point. Such information is important for further optical detection of spin related phenomena driven by vicinity of compensation point in nanostructures containing GdFe.

Room-temperature synthesis and optical properties of nanostructured Ba-Doped ZnO thin films

2019 ◽  
Vol 130 ◽  
pp. 321-331 ◽  
Author(s):  
C.C. Okorieimoh ◽  
Ugochi Chime ◽  
Agnes C. Nkele ◽  
Assumpta C. Nwanya ◽  
Itani Given Madiba ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Room Temperature ◽  
Zno Thin Films ◽  
Temperature Synthesis ◽  
Room Temperature Synthesis ◽  
Doped Zno

Effect of pH on the structural and optical properties of polycrystalline ZnSe thin films produced by CBD method

2019 ◽  
Vol 33 (05) ◽  
pp. 1950024 ◽  
Author(s):  
Fatma Meydaneri Tezel ◽  
İ. Afşin Kariper
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Room Temperature ◽  
Dielectric Constants ◽  
Structural And Optical Properties ◽  
Polycrystalline Structure ◽  
Density Values ◽  
Cbd Method ◽  
Znse Thin Films ◽  
Absorbance Spectra

In this study, zinc selenide (ZnSe) thin films were produced on glass substrate by using chemical bath deposition (CBD) method at 80[Formula: see text]C, from aqueous solutions of zinc sulphate and sodium selenosulphide, which were produced using solid selenium as the selenium source. The optical and structural properties of ZnSe thin films were investigated at room-temperature. The pH of the chemical bath, in which ZnSe thin films were immersed, were changed between pH:8–11. Optical properties of the films, including extinction coefficient, refractive index, reflectance, absorbance, transmittance, dielectric constants and optical density values were calculated using absorbance and transmittance measurements determined using a Hach Lange 500 spectrophotometer, in 300–1100 nm wavelength range. Optical bandgap values were obtained from transmittance and absorbance spectra ranged between 2.12 and 2.49 eV. According to XRD results, it was found that the films have polycrystalline structure and they exhibited different film thicknesses depending on phase and pH changes.

scholarly journals Optical properties of CuSe thin films - band gap determination

2017 ◽  
Vol 49 (2) ◽  
pp. 167-174 ◽  
Author(s):  
Milica Petrovic ◽  
Martina Gilic ◽  
Jovana Cirkovic ◽  
Maja Romcevic ◽  
Nebojsa Romcevic ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Band Gap ◽  
Room Temperature ◽  
Nir Spectroscopy ◽  
Copper Selenide ◽  
Photoluminescence Spectra ◽  
Indirect Transition ◽  
Direct Transition ◽  
Scanning Electron

Copper selenide thin films of three different thicknesses have been prepared by vacuum evaporation method on a glass substrate at room temperature. The optical properties of the films were investigated by UV-VIS-NIR spectroscopy and photoluminescence spectroscopy. Surface morphology was investigated by field-emission scanning electron microscopy. Copper selenide exhibits both direct and indirect transitions. The band gap for direct transition is found to be ~2.7 eV and that for indirect transition it is ~1.70 eV. Photoluminescence spectra of copper selenide thin films have also been analyzed, which show emission peaks at 530, 550, and 760 nm. The latter corresponds to indirect transition in investigated material.

Analyzing TEM Images for Accurate Determination of Lattice Parameters of Vacuum Evaporated SnSe Thin Film by Image Processing Software

2016 ◽  
Vol 1141 ◽  
pp. 51-53
Author(s):  
Chetan Zankat ◽  
V.M. Pathak ◽  
Pratik Pataniya ◽  
G.K. Solanki ◽  
K.D. Patel ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Image Processing ◽  
Optical Properties ◽  
Room Temperature ◽  
Accurate Determination ◽  
Lattice Parameters ◽  
Processing Software ◽  
Image Processing Software

Amorphous SnSe thin films were deposited by thermal evaporation technique on glass substrates kept at room temperature in a vacuum better than 10-5Torr. A detailed study of structural and optical properties of 150 nm thin film was carried out. The selected area diffraction patterns obtained by TEM for this thin film were analyzed by a new method that involves accurate determination of lattice parameters by image processing software. The obtained results are in good agreement with the JCPDS data. Optical transmission spectra obtained at room temperature were analyzed to study optical properties of deposited thin films. It has been found that indirect carrier transition is responsible for optical absorption process in the deposited thin films.

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