Raman and Photoluminescence Studies of Undoped and Magnesium-Doped Gan Films on Sapphire

1994 ◽  
Vol 339 ◽  
Author(s):  
Jaime A. Freitas ◽  
M. Asif Khan
Keyword(s):  
Room Temperature ◽  
Growth Direction ◽  
High Crystalline Quality ◽  
Photoluminescence Study ◽  
Recombination Processes ◽  
Scattering Measurements ◽  
Donor Acceptor ◽  
Intense Emission ◽  
Photoluminescence Studies ◽  
Mg Doped

ABSTRACTRoom temperature Raman scattering measurements performed on undoped GaN films indicate that high crystalline quality wurtzite material has been deposited on the basal plane of sapphire. Photoluminescence study of these films show that thicker films (t > 4μm) are homogeneous along the growth direction. The PL spectra of Mg-doped films are dominated by an intense emission band around 3.1 eV associated with recombination processes involving donor-acceptor pairs.

Photoluminescence Studies of p-type GaN:Mg Co-doped with Oxygen

2000 ◽  
Vol 639 ◽  
Author(s):  
R. Y. Korotkov ◽  
J. M. Gregie ◽  
B. W. Wessels
Keyword(s):  
Low Temperature ◽  
Integrated Intensity ◽  
Donor Acceptor ◽  
Photoluminescence Studies ◽  
P Type ◽  
Formation Energies ◽  
Different Origin ◽  
Co Doped ◽  
Low Temperature Photoluminescence ◽  
Mg Doped

ABSTRACTThe low temperature photoluminescence (PL) of Mg-doped GaN co-doped with oxygen is investigated. Two PL bands are observed at low temperature at 2.5 and 2.8 eV in the p-type oxygen co-doped samples. Both the 2.5 eV and 2.8 eV bands are attributed to donor-acceptor (DA) transitions involving deep donors of different origin and a shallow MgGa acceptor. The integrated intensity of the 2.8 eV band in p-type GaN decreases as the oxygen partial pressure is increased. The decrease is attributed to reduced compensation by deep native donors. The two bands are not formed in n-type (n > 1019 cm−3) GaN:Mg over-doped with oxygen indicating that the deep donors responsible for these transitions have high formation energies in n-type material.

scholarly journals Thermochromic aggregation-induced dual phosphorescence via temperature-dependent sp3-linked donor-acceptor electronic coupling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tao Wang ◽  
Zhubin Hu ◽  
Xiancheng Nie ◽  
Linkun Huang ◽  
Miao Hui ◽  
...  
Keyword(s):  
Excited State ◽  
Room Temperature ◽  
Electronic Coupling ◽  
Temperature Dependent ◽  
Molecular Systems ◽  
Donor And Acceptor ◽  
Theoretical Investigations ◽  
Donor Acceptor ◽  
And Control ◽  
Two Temperature

AbstractAggregation-induced emission (AIE) has proven to be a viable strategy to achieve highly efficient room temperature phosphorescence (RTP) in bulk by restricting molecular motions. Here, we show that by utilizing triphenylamine (TPA) as an electronic donor that connects to an acceptor via an sp3 linker, six TPA-based AIE-active RTP luminophores were obtained. Distinct dual phosphorescence bands emitting from largely localized donor and acceptor triplet emitting states could be recorded at lowered temperatures; at room temperature, only a merged RTP band is present. Theoretical investigations reveal that the two temperature-dependent phosphorescence bands both originate from local/global minima from the lowest triplet excited state (T1). The reported molecular construct serves as an intermediary case between a fully conjugated donor-acceptor system and a donor/acceptor binary mix, which may provide important clues on the design and control of high-freedom molecular systems with complex excited-state dynamics.

scholarly journals Structure and Properties of Ln2MoO6 Oxymolybdates (Ln = La, Pr, Nd) Doped with Magnesium

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 611
Author(s):  
Ekaterina Orlova ◽  
Elena Kharitonova ◽  
Timofei Sorokin ◽  
Alexander Antipin ◽  
Nataliya Novikova ◽  
...  
Keyword(s):  
Rare Earth ◽  
Infrared Spectroscopy ◽  
Room Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Spectroscopy Data ◽  
Structure And Properties ◽  
Hygroscopic Properties ◽  
Thermogravimetric Studies ◽  
Mg Doped

The literature data and the results obtained by the authors on the study of the structure and properties of a series of polycrystalline and single-crystal samples of pure and Mg-doped oxymolybdates Ln2MoO6 (Ln = La, Pr, Nd) are analyzed. Presumably, the high-temperature phase I41/acd of Nd2MoO6 single crystals is retained at room temperature. The reason for the loss of the center of symmetry in the structures of La2MoO6 and Pr2MoO6 and the transition to the space group I4¯c2 is the displacement of oxygen atoms along the twofold diagonal axes. In all structures, Mg cations are localized near the positions of the Mo atoms, and the splitting of the positions of the atoms of rare-earth elements is found. Thermogravimetric studies, as well as infrared spectroscopy data for hydrated samples of Ln2MoO6 (Ln = La, Pr, Nd), pure and with an impurity of Mg, confirm their hygroscopic properties.

Mechanical properties of NiAl-Mo composites produced by specially controlled directional solidification

2012 ◽  
Vol 1516 ◽  
pp. 255-260 ◽  
Author(s):  
G. Zhang ◽  
L. Hu ◽  
W. Hu ◽  
G. Gottstein ◽  
S. Bogner ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Directional Solidification ◽  
Creep Resistance ◽  
Room Temperature ◽  
Growth Direction ◽  
Nominal Composition ◽  
Potential Candidate ◽  
In Situ Composites

ABSTRACTMo fiber reinforced NiAl in-situ composites with a nominal composition Ni-43.8Al-9.5Mo (at.%) were produced by specially controlled directional solidification (DS) using a laboratory-scale Bridgman furnace equipped with a liquid metal cooling (LMC) device. In these composites, single crystalline Mo fibers were precipitated out through eutectic reaction and aligned parallel to the growth direction of the ingot. Mechanical properties, i.e. the creep resistance at high temperatures (HT, between 900 °C and 1200 °C) and the fracture toughness at room temperature (RT) of in-situ NiAl-Mo composites, were characterized by tensile creep (along the growth direction) and flexure (four-point bending, vertical to the growth direction) tests, respectively. In the current study, a steady creep rate of 10-6s-1 at 1100 °C under an initial applied tensile stress of 150MPa was measured. The flexure tests sustained a fracture toughness of 14.5 MPa·m1/2at room temperature. Compared to binary NiAl and other NiAl alloys, these properties showed a remarkably improvement in creep resistance at HT and fracture toughness at RT that makes this composite a potential candidate material for structural application at the temperatures above 1000 °C. The mechanisms responsible for the improvement of the mechanical properties in NiAl-Mo in-situ composites were discussed based on the investigation results.

Thermal Strain Study of Almost Lattice-Matched Epitaxial InuGa1-uAs1-vP1-v Films on InP(100) Substrates

1989 ◽  
Vol 160 ◽  
Author(s):  
G. Bai ◽  
M-A. Nicolet ◽  
S.-J. Kim ◽  
R.G. Sobers ◽  
J.W. Lee ◽  
...  
Keyword(s):  
Room Temperature ◽  
Epitaxial Film ◽  
Lattice Mismatch ◽  
Thermal Strain ◽  
Growth Direction ◽  
Epitaxial Films ◽  
Double Crystal ◽  
X Ray ◽  
Lattice Matched ◽  
Coherent Interfaces

AbstractSingle layers of ~ 0.5µm thick InuGa1-uAs1-vPv (0.52 < u < 0.63 and 0.03 < v < 0.16) were grown epitaxially on InP(100) substrates by liquid phase epitaxy at ~ 630°C. The compositions of the films were chosen to yield a constant banndgap of ~ 0.8 eV (λ = 1.55 µm) at room temperature. The lattice mismatch at room temperature between the epitaxial film and the substrate varies from - 4 × 10-3 to + 4 × 10-3. The strain in the films was characterized in air by x-ray double crystal diffractometry with a controllable heating stage from 23°C to ~ 700°C. All the samples have an almost coherent interfaces from 23°C to about ~ 330°C with the lattice mismatch accomodated mainly by the tetragonal distortion of the epitaxial films. In this temperature range, the x-ray strain in the growth direction increases linearly with temperature at a rate of (2.0 ± 0.4) × 10-6/°C and the strain state of the films is reversible. Once the samples are heated above ~ 300°C, a significant irreversible deterioration of the epitaxial films sets in.

scholarly journals Regioisomeric Effect on the Excited-State Fate Leading to Room-Temperature Phosphorescence or Thermally Activated Delayed Fluorescence in a Dibenzophenazine-Cored Donor–Acceptor–Donor System

2021 ◽  
Author(s):  
Takumi Hosono ◽  
Nicolas Oliveira Decarli ◽  
Paola Zimmermann Crocomo ◽  
Tsuyoshi Goya ◽  
Leonardo Evaristo de Sousa ◽  
...  
Keyword(s):  
Excited State ◽  
Room Temperature ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Room Temperature Phosphorescence ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Donor Acceptor ◽  
Emission Behavior

Exploring design principle for switching thermally activated dealyed fluorescecne (TADF) and room temperature phosphorescence (RTP) is a fundamentally imporant research in developing triplet-mediated photofunctional organic materials. Herein systematic studies on the regioisomeric and substituents effects in a twisted donor–acceptor–donor (D–A–D) scaffold (A = dibenzo[a,j]phenazine; D = dihydrophenazasiline) on the fate of the excited state have been performed. The study revealed that the regiosiomerism clearly affects the emission behavior of the D–A–D compounds. Distinct difference in TADF, dual TADF & RTP, and dual RTP were observed, depending on the host used. Furthermore, OLED organic light-emitting diodes (OLEDs) fabricated with the developed emitters achieved high external quantum yields for RTP-based OLEDS up to 7.4%.

scholarly journals Sintesis dan Analisis Penambahan Doping Magnesium (Mg) pada Material Superkonduktor FeSe dengan Metode Reaksi Padatan dalam Tabung Tertutup

2019 ◽  
Vol 19 (2) ◽  
pp. 89-94
Author(s):  
Muhammad Ilham Maulana
Keyword(s):  
Room Temperature ◽  
Industrial Revolution ◽  
Stoichiometric Composition ◽  
Solid State Reaction Method ◽  
Superconducting Materials ◽  
Superconducting Material ◽  
Critical Temperature Tc ◽  
Properties Of Superconductors ◽  
Very High ◽  
Mg Doped

[ID] Ketergantungan manusia terhadap teknologi memasuki Revolusi Industri 4.0 sangat tinggi. Contoh penerapan inovasi di bidang teknologi informasi salah satunya adalah superkomputer dari material superkonduktor. Material superkonduktor identik dengan material non ferromagnetik karena sifatnya diamagnetis sempurna. Namun, sejak ditemukannya material superkonduktor berbasis logam ferromagnetik, penelitian terus dikembangkan, salah satunya material FeSe. Beberapa parameter yang perlu diperhatikan pada pembuatan material FeSe untuk memperoleh sifat superkonduktor terbaiknya diantaranya komposisi stoikiometri, penambahan doping, dan proses pembuatan material FeSe seperti proses pemaduan dan sintering. Dalam penelitian ini, pengaruh variasi doping Mg akan dianalisis terhadap sifat superkonduktor, morfologi, dan fasa yang terbentuk pada material superkonduktor FeSe. Material FeSe dibuat dengan metode reaksi padatan dalam tabung tertutup (Powder in Sealed Tube) secara insitu. Temperatur sintering yang digunakan 845⁰C yang ditahan selama 6 jam, dengan kenaikan temperatur 7⁰C/menit dari temperatur kamar, dan laju pendinginan normalizing. Kandidat material superkonduktor terbaik terdapat pada sampel Mg0.01Fe0.99Se. Didapatkan Temperatur kritis (Tc)onset = 15.42 K dan Tczero = 5.4 K. Morfologi sampel menunjukkan kristalisasi besar. Lalu, persentase fraksi volume fasa superkonduktornya juga merupakan yang terbesar yaitu 81.99%. [EN] Human dependence on technology into the Industrial Revolution 4.0 is very high. Example, the application of innovations in information technology is supercomputer from superconducting materials. Superconducting materials are identical from non-ferromagnetic materials because tend perfectly diamagnetic. However, since ferromagnetic-metal-based superconducting material discovered, research continues to be developed, like FeSe material. Some parameters that need to be considered in making FeSe material to obtain the best superconductor properties include stoichiometric composition, doping addition, and process of making FeSe materials like synthesis and sintering treatment. In this study, the effect of Mg-doped variations will be analyzed towards properties of superconductors, morphology, and phases formed in FeSe superconducting materials. MgxFe1-xSe made by solid-state reaction method in sealed tube (Powder in Sealed Tube) “insituely”. The sintering temperature used 845⁰C which held for 6 hours, with 7⁰C/minute temperature rise from room-temperature and normalizing cooling rate used. The best candidate superconducting material came from Mg0.01Fe0.99Se, obtained critical temperature (Tc)onset = 15.42 K, and Tczero = 5.4 K. Sample morphology shows a large crystallization. Then, the percentage fraction of the superconducting phase was also the largest, which is 81.99%.

Mechanism of donor–acceptor pair recombination in Mg-doped GaN epilayers grown on sapphire substrates

1998 ◽  
Vol 84 (4) ◽  
pp. 2082-2085 ◽  
Author(s):  
T. W. Kang ◽  
S. H. Park ◽  
H. Song ◽  
T. W. Kim ◽  
G. S. Yoon ◽  
...  
Keyword(s):  
Acceptor Pair ◽  
Sapphire Substrates ◽  
Donor Acceptor ◽  
Donor Acceptor Pair ◽  
Mg Doped
Sign in / Sign up

Export Citation Format

Share Document