Annealing behavior of hexagonal phase content in cubic GaN thin films grown on GaAs (001) by MOCVD

The annealing behavior of the hexagonal phase content in cubic GaN (c-GaN) thin films grown on GaAs (001) by MOCVD is reported. C-GaN thin films are grown on GaAs (001) substrates by metalorganic chemical vapor deposition (MOCVD). High temperature annealing is employed to treat the as-grown c-GaN thin films. The characterization of the c-GaN films is investigated by photoluminescence (PL) and Raman scattering spectroscopy. The change conditions of the hexagonal phase content in the metastable c-GaN are reported. There is a boundary layer existing in the c-GaN/GaAs film. When being annealed at high temperature, the intensity of the TOB and LOB phonon modes from the boundary layer weakens while that of the E-2 phonon mode from the hexagonal phase increases. The content change of hexagonal phase has closer relationship with annealing temperature than with annealing time period.

Annealing behaviors of photoluminescence from SiOx : H

The strong photoluminescence (PL) of SiOx:H prepared by plasma enhanced chemical vapor deposition has been systematically studied in conjunction with infrared and micro-Raman spectra. We have found that each PL spectrum is comprised of two Gaussian components, a main band and a shoulder. The main band might originate from amorphous silicon clusters embedded in die SiOx network, and its redshift with annealing temperature is due to expansion of the silicon clusters. The shoulder remains at about 835 nm in spite of the annealing temperature and possibly comes from luminescent defect centers. The enhanced PL spectra after 1170 degrees C annealing are attributed to the quantum confinement effects of nanocrystalline silicon embedded in the SiO2 matrix. (C) 1998 American Institute of Physics.

Effect of noncoherent islands on the optical properties of the 1.3 mu m InAs/GaAs quantum dots during rapid thermal annealing

The effect of thermal annealing of InAs/GaAs quantum dots (QDs) with emission wavelength at 1.3 mu m have been investigated by photoluminescence (PL) and transmission electron microscopy (TEM measurements. There is a dramatic change in the A spectra when the annealing temperature is raised up to 800 degrees C: an accelerated blushifit of the main emission peak of QDs together with an inhomogeneous broadening of the linewidth. The TEM images shows that the lateral size of normal QDs decreases as the annealing temperature is increased, while the noncoherent islands increase their size and densit. A small fraction of the relative large QDs contain dislocations when the annealing temperature increases up to 800 degrees C. The latter leads to the strong decrease of the PL intensity.

Effects of annealing treatment on the formation of CO2 in ZnO thin films grown by metal-organic chemical vapor deposition

Post-growth annealing was carried out on ZnO thin films grown by metal-organic chemical vapor deposition (MOCVD). The grain size of ZnO thin film increases monotonically with annealing temperature. The ZnO thin films were preferential to c-axis oriented after annealing as confirmed by Xray diffraction (XRD) measurements. Fourier transformation infrared transmission measurements showed that ZnO films grown at low temperature contains CO2 molecules after post-growth annealing. A two-step reaction process has been proposed to explain the formation mechanism of CO2, which indicates the possible chemical reaction processes during the metal-organic chemical vapor deposition of ZnO films.

RECRYSTALLIZATION, IMPURITY MIGRATION AND OPTICAL ACTIVATION OF YB-IMPLANTED SILICON INDUCED BY RAPID THERMAL ANNEALING

The rapid thermal annealing temperature dependence of the recrystallization, Yb migration and its optical activation were studied for Yb-implanted silicon. For the annealing regime 800-1000-degrees-C, the Yb segregates both at the crystal/amorphous interface and at the surface, which is different from the usual segregation of Er at the crystal/amorphous interface, and the efficiency of optical activation also increases with annealing temperature. However, the amorphous layer regrows completely and no photoluminescence is observed after the annealing at 1200-degrees-C.

INTERACTION OF CO WITH SI AND SIO2 DURING RAPID THERMAL ANNEALING

The interaction of Co with Si and SiO2 during rapid thermal annealing has been investigated. Phase sequence, layer morphology, and reaction kinetics were studied by sheet resistance, x-ray diffraction, Auger electron spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy. With increasing annealing temperature, Co film on Si(100) is transformed sequentially into Co2Si, CoSi, and finally CoSi2 which corresponds to the minimum of sheet resistance. No evidence of silicide formation was observed for Co/SiO2 annealed even at the high temperature of 1050-degrees-C.

Rapid thermal annealing of arsenic implanted Si1-xGex epilayers

Rapid thermal annealing of arsenic implanted Si1-xGex was studied by secondary ion-mass spectroscopy (SIMS) and spreading resistance probe (SRP) over a wide range of Ge fractions (0-43%). Redistribution of the implanted arsenic was followed as a function of Ge content and annealing temperature. Arsenic concentration profiles from SIMS indicated that the behavior of implanted arsenic in Si1-xGex after RTA was different from that in Si, and the Si1-xGex samples exhibited box-shaped, concentration-dependent diffusion profiles with increasing Ge content. The maximum concentrations of electrically active arsenic in Si1-xGex was found to decrease with increasing Ge content. Experimental results showed that the arsenic diffusion is enhanced with increasing temperature for certain Ge content and strongly dependent on Ge content, and the higher Ge content, the faster As diffusion.

Dependence of wet etch rate on deposition, annealing conditions and etchants for PECVD silicon nitride film

The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition (PECVD) silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiN_x:H by HF solution. A low etch rate was achieved by increasing the SiH_4 gas flow rate or annealing temperature, or decreasing the NH_3 and N_2 gas flow rate. Concen-trated, buffered, and dilute hydrofluoric acid were utilized as etchants for SiO_2 and SiN_x:H. A high etching selectivity of SiO_2 over SiN_x:H was obtained using highly concentrated buffered HF.

Effect of Annealing on Structural and Magnetic Properties of a Thick (Ga,Mn)As Layer

We investigate effects of annealing on magnetic properties of a thick (Ga,Mn)As layer, and find a dramatic increase of the Curie temperature from 65 to 115 K by postgrowth annealing for a 500-nm (Ga,Mn)As layer. Auger electron spectroscopy measurements suggest that the increase of the Curie temperature is mainly due to diffusion of Mn interstitial to the free surface. The double-crystal x-ray diffraction patterns show that the lattice constant of (Ga,Mn)As decreases with increasing annealing temperature. As a result, the annealing induced reduction of the lattice constant is mainly attributed to removal of Mn interstitial.

Charge-sensitive deep level transient spectroscopy of helium-ion-irradiated silicon, as-irradiated and after thermal annealing

Electrically active defects in the phosphor-doped single-crystal silicon, induced by helium-ion irradiation under thermal annealing, have been investigated. Isothermal charge-sensitive deep-level transient spectroscopy was employed to study the activation energy and capture cross-section of helium-induced defects in silicon samples. It was shown that the activation energy levels produced by helium-ion irradiation first increased with increasing annealing temperature, with the maximum value of the activation energy occurring at 873K, and reduced with further increase of the annealing temperature. The energy levels of defects in the samples annealed at 873 and 1073K are found to be located near the mid-forbidden energy gap level so that they can act as thermally stable carrier recombination centres.

The influence of the microstructure evolution on the surface morphology in the annealing process of helium-implanted spinel

Single-crystalline spinel (MgAl2O4) specimens were implanted with helium ions of 100 keV at three successively increasing fluences of (0.5, 2.0 and 8.0) x 10(16) ions/cm(2) at room temperature. The specimens were subsequently annealed in vacuum at different temperatures ranging from 500 to 1100 degrees C. Different techniques, including Fourier transformed infrared spectroscopy (FTIR), thermal desorption spectrometry (TDS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the specimens, It was found that the absorbance peak in the FTIR due to the stretching vibration of the Al-O bond shifts to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with an increase of annealing temperature. The absorbance peak shift has a linear relationship with the fluence increase in the as-implanted state, while it does not have a linear relationship with the fluence increase after the annealing process. Surface deformation occurred in the specimens implanted with fluences of 2.0 and 8.0 x 10(16) ions/cm(2) in the annealing process. The phenomena described above can be attributed to differences in defect formation in the specimens. (C) 2008 Elsevier B.V. All rights reserved.

Annealing effects in silicon implanted with helium

Silicon samples were implanted with helium and analyzed by atomic force microscopy (AFM) and Raman spectroscopy before and after annealing in the range of 523-1273 K. After annealing at 523 K, the amorphous area induced by He-ion implantation at room temperature was partially recovered and grain sizes became larger. The surface morphology was analyzed through AFM measurements and it was observed that root mean square of the surface roughness alters upwards and then downwards with annealing temperature. (C) 2008 Elsevier B.V. All rights reserved.

Effects of annealing on the photoluminescence of He ion implanted sapphire after 230-MeV Pb ion irradiation

Single crystal sapphire (Al2O3) samples implanted with 110 keV He and irradiated at 320 K by Pb-208(27), ions with energy of 1.1 MeV/u to the fluences ranging from 1 X 10(12) to 5 X 10(14) ion/cm(2) and subsequently annealed at 600, 900 and 1100 K. The obtained PL spectra showed that emission peaks centred at 375, 390, 413, and 450 nm appeared in irradiated samples. The peak of 390 ran became very intense after 600 K annealing. The peak of 390 nm weakened and 510 nm peak started to build up at 900 K annealing, the peak of 390 nm vanished and 510 nm peak increased with the annealing temperature rising to 1100 K. Infrared spectra showed a broadening of the absorption band between 460 cm(-1), and 510 cm(-1) indicating strongly damaged regions being formed in the Al2O3 samples and position shift of the absorption band at 1000-1300 cm(-1) towards higher wavenumber after Pb irradiation.

Enhanced photoluminescence of Ar+ implanted sapphire before and after annealing

In this paper, we studied the changes in the photoluminescence spectra of the Ar+ ion implanted monocrystalline sapphire annealed at different atmospheres and different temperatures. Single crystals of sapphire (Al2O3) with the (1 0 (1) over bar 0) (m-samples) orientation were implanted at 623 K with 110 keV Ar+ ions to a fluence of 9.5 x 10(16) ions/cm(2). Photoluminescence measurement of the as-implanted sample shows a new emission band at 506 nm, which is attributed to the production of interstitial Al atoms. The intensity of emission band at 506 nm first increased then decreased with increase in annealing temperature. For the same annealing temperature, the intensity of PL peak at 506 nm of the sample annealed in air was higher than the sample annealed in vacuum. The experimental results show that the intensity of the PL peak at 506 nm of Ar-implanted sapphire can be enhanced by subsequent annealing with an enhancement of nearly 20 times. The influence of thermal annealing of the Ar-implanted samples on the new 506 nm emission band was discussed. (C) 2009 Elsevier B.V. All rights reserved.

Effect of substrate and annealing on the structural and optical properties of ZnO:Al films

ZnO:Al thin films with c-axis preferred orientation were deposited on glass and Si substrates using RF magnetron sputtering technique. The effect of substrate on the structural and optical properties of ZnO:Al films were investigated. The results showed a strong blue peak from glass-substrate ZnO:Al film whose intensity became weak when deposited on Si substrate. However, the full width at half maxima (FWHM) of the Si-substrate ZnO:Al (0 0 2) peaks decreased evidently and the grain size increased. Finally, we discussed the influence of annealing temperature on the structural and optical properties of Si-substrate ZnO:Al films. After annealing, the crystal quality of Si-substrate ZnO:Al thin films was markedly improved and the intensity of blue peak (similar to 445 nm) increased noticeably. This observation may indicate that the visible emission properties of the ZnO:Al films are dependent more on the film crystallinity than on the film stoichiometry. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.