Keywords : annealing

Principles and practices of Si light emitting diodes using dressed photons

M. Ohtsu; T. Kawazoe

Advanced Materials Letters, 2019, Volume 10, Issue 12, Pages 860-867
DOI: 10.5185/amlett.2019.2264

This paper reviews basic research and technical developments on silicon (Si) light-emitting diodes (Si-LEDs) fabricated by using a novel dressed-photon–phonon (DPP)-assisted annealing method. These devices exhibit unique light emission spectral profiles in the wavelength range 900–2500 nm, including novel photon breeding features. The highest optical output power demonstrated was as high as 2.0 W. It is pointed out that boron (B) atoms, serving as p-type dopants, formed pairs whose length was three-times the lattice constant of the host Si crystal. These B atom pairs are the origin of the photon breeding. It is pointed out that photon breeding took place with respect to photon spin. Furthermore, recent measurements show that the B atom pairs tend to form a chain-like configuration. Copyright © VBRI Press. 

Post-deposition Annealing Controlled Structural And Optical Properties Of RF Magnetron Sputtered MoO3 Films

S. Subbarayudu; V. Madhavi;S. Uthanna

Advanced Materials Letters, 2013, Volume 4, Issue 8, Pages 637-642
DOI: 10.5185/amlett.2012.11466

MoO3 films were deposited on Corning glass and silicon substrates held at room temperature (303 K) by RF magnetron sputtering of metallic molybdenum target at a fixed oxygen partial pressure of 4x10 -4 mbar and sputter pressure of 4x10 -2 mbar. The as deposited films were annealed in air at different temperatures in the range 473 – 673 K. X-ray diffraction studies suggest that the as-deposited and the films annealed at 473 K were amorphous in nature, while those annealed at 573 and 673 K were polycrystalline with mixed phases of α- orthorhombic and β- monoclinic MoO3. Scanning electron microscope images of the films annealed at 573 and 673 K exhibited nanoflower like and nanodisk like structures due to improvement in the crystallinity. Fourier transform infrared studies showed the characteristic vibrations of MoO3 with shift in the vibrational modes of Mo = O and Mo – O – Mo with increase of annealing temperature. The optical absorption edge of the films shifted towards lower wavelengths side with increase of annealing temperature. Optical band gap of as-deposited films was 2.98 eV with refractive index 2.01, while those annealed at 673 K showed the optical band gap of 3.15 eV and refractive index of 2.08. The MoO3 films annealed at 673 K were of nanocrystalline with crystallite size of 39 nm with optical band gap of 3.15 eV and refractive index of 2.08 were favorable for electron blocking and hole-selective layers in bulk-heterojuction solar cells.

Modification Of Nanocrystalline RF Sputtered Tin Oxide Thin Film Using SHI Irradiation

Vijay Kumara; Anshul Jaina; Deepti Pratapa; D.C. Agarwalb; I. Sulaniab; V. V. Siva Kumarb; A. Tripathib; S. Varmac; R.S. Chauhan

Advanced Materials Letters, 2013, Volume 4, Issue 6, Pages 428-432
DOI: 10.5185/amlett.2012.ib.108

Nano crystalline tin oxide thin films were deposited on Si and quartz substrates using R. F. magnetron sputtering technique. A set of films was annealed in oxygen environment. These as-deposited and annealed films were irradiated using 100 MeV Ag ions at different fluences ranging from 3×10 11 to 3×10 13 ions/cm 2 . The structural, optical and surface morphological properties of films were studied using X-ray diffraction (XRD), UV-Vis spectroscopy, and atomic force microscopy (AFM) techniques. As deposited films showed the polycrystalline nature and annealing enhances the crystallinity along a particular plane. Upon irradiation at lower fluences up to 3×1012 ions/cm 2 , reduction in crystallinity is observed but at highest fluence 1×10 13 ions/cm 2 a small increase in crystallinity occurs as inferred from XRD spectra. UV-Vis study showed red shift at the lower fluences and blue shift at higher fluences. The pristine film, as observed in AFM micrograph, has randomly distributed surface nano structures with broader size distribution. Irradiation induces the formation of regular shape structures with narrow size distribution. These results may be attributed to the energy deposited by swift heavy ions in the film.

Effect Of Annealing Temperature On Structural Properties Of nanocrystalline Tl3(PW12O40) Thin Films

S.R. Mane; P.S. Patil;P. N. Bhosale; R. M. Mane

Advanced Materials Letters, 2013, Volume 4, Issue 1, Pages 94-98
DOI: 10.5185/amlett.2013.icnano.117

Thallium (I) doped tungsten heteropolyoxometalate (HPOM) combinatorial thin films have been deposited on glass substrate using simple chemical bath deposition technique. The deposited films were annealed at 100 o C, 150 o C, 200 o C and 250 o C. These annealed thin films were characterized by using SEM, EDAX, AFM, FT-IR, XRD and TGA-DTA techniques for their structural properties. SEM and EDAX results shows that, tungsten HPOM material is polycrystalline in nature and Tl (I) is intercalated in phosphotungustate anion. AFM studies on the films annealed at different temperatures reveal that the surface roughness increases with the increase in annealing temperature, suggesting an increase of crystallization with temperature. FT-IR study confirms the well formation of heteropolyoxometalate material under investigation. Various structural parameters such as lattice constants, crystallite size and grain size have been calculated and they are found temperature dependent. The lattice constant, crystallite size and grain size of tungsten HPOM material increases with increase in temperature. XRD pattern of annealed thin films shows better crystanality of tungsten HPOM material having simple cubic spinel structure. The TGA-DTA study revealed that, Tl3 (PW12 O40) material is thermally stable up to 265.12 o C.

Ferromagnetism In Inhomogeneous Bulk samples Of Co-doped ZnO

V. K. Sharma; M. Najim; G. D. Varma

Advanced Materials Letters, 2012, Volume 3, Issue 2, Pages 107-111
DOI: 10.5185/amlett.2011.6276

We report on the effect of different gaseous environments (air, argon and Ar/H2) on the structural and magnetic properties of Zn0.98Co0.02O synthesized by the solid state reaction route. We have also studied the effect of different annealing times and temperatures on the as synthesized samples. M-H curves of the air sintered and the argon annealed samples show paramagnetic behavior whereas the samples annealed in the hydrogenated argon (Ar/H2) environment exhibit ferromagnetic property at room temperature. Based on the structural and magnetic properties it has been found that Co metal clusters are responsible for the observed room temperature ferromagnetism (RTFM) in the hydrogenated samples.

Fe Clusters As Origin Of Ferromagnetism In Hydrogenated Zn1-xFexO (x= 0.02 & 0.05) Samples

V. K. Sharma; G.D. Varma

Advanced Materials Letters, 2012, Volume 3, Issue 2, Pages 126-129
DOI: 10.5185/amlett.2011.7283

Bulk samples of Zn1-xFexO (x=0.02 and 0.05) were synthesized via solid state reaction route by sintering in air at 800 o C. Some sintered samples were annealed in Ar/H2 at 800 o C for ~ 5 hrs. X-ray diffraction results reveal that the basic crystal structure of the as sintered and hydrogenated (Ar/H2) samples corresponds to ZnO wurtzite structure together with some traces of ZnFe2O4 in the as sintered and Fe metal in the hydrogenated samples. The as sintered samples of both compositions show paramagnetic behaviour and after hydrogenation they exhibit ferromagnetic interactions at room temperature. Increase in the electrical conductivity has also been observed in the hydrogenated samples. The presence of small Fe clusters in the hydrogenated samples are expected to be responsible for the observed room temperature ferromagnetism.