镱铒共掺Al2O3薄膜激光退火研究

讨论了激光退火工艺参量对镱铒共掺Al2O3薄膜表面形貌和退火均匀性的影响。薄膜样品被置放于衰减扩束透镜的3倍焦距位置时,薄膜上8 mm半径区域内近似均匀退火;退火时间为32 s时,表面形貌与退火前基本相同。阈值退火功率为5 W,最佳退火功率为20 W。对相同工艺制备的镱铒共掺Al2O3薄膜分别进行CO2激光退火和热退火处理,光致发光(PL)谱测量表明,前者峰值强度比后者强10倍以上,并且热退火光致发光强度随抽运功率增加出现饱和、下降,而激光退火近似随抽运功率单调线性增强。     

Photo and thermally induced properties change in Bi/Ag/Se trilayer thin film

In this article, we have demonstrated the optical and structural properties change in Bi/Ag/Se trilayer thin films by the influence of thermal and photon energy. The trilayer films prepared by thermal evaporation technique were annealed and laser irradiated at room temperature. The X-ray diffraction study revealed the Ag₂Se phase formation and the surface morphology change is being studied by Field emission scanning electron microscopy. The optical properties of the studied films were characterized by using FTIR spectrophotometer in the wavelength range 400–1200?nm. The reduction of optical band gap by both thermal and laser irradiation is being discussed on the basis of chemical disorderness, defect states and density of localized states in the mobility gap. The Raman shift due to annealing and irradiation supports the changes in the film. The large change in optical band gap in thermal annealing is useful for memory device and waveguide fabrication.     

Structural and optical properties of Si/SiO2 multi-quantum wells

Structural and optical properties of Si/SiO₂ multi-quantum wells (MQW) were investigated by means of Raman scattering and photoluminescence (PL) spectroscopy. The MQW structures were fabricated on a quartz substrate by remote plasma enhanced chemical vapour deposition (RPECVD) of alternating amorphous Si and SiO₂ layers. After layer deposition the samples were subjected to heat treatments, i.e. rapid thermal annealing (RTA) and furnace annealing. Distinct PL signatures of confined carriers evidenced formation of Si-nanocrystals (nc-Si) in annealed samples. Analyses of Raman spectra also show presence of nc-Si phase along with amorphous-Si (a-Si) phase in the samples. The strong influence of the annealing parameters on the formation of nc-Si phase suggests broad possibilities in engineering MQW with various optical properties. Interestingly, conversion of the a-Si phase to the nc-Si phase saturates after certain time of furnace annealing. On the other hand, thinner Si layers showed a disproportionately lower crystalline volume fraction. From the obtained results we could assume that an interface strain prevents full crystallization of the Si layers and that the strain is larger for thinner Si layers. The anomalous dependence of nc-Si Raman scattering peak position on deposited layer thickness observed in our experiments also supports the above assumption.     

Cathodoluminescence of laser-annealed erbium-implanted zinc selenide

After zinc selenide crystals implanted with erbium ions had been annealed with a continuous wave (cw) krypton ion laser it was found that the cathodoluminescence emission intensity of the implanted erbium ions had been considerably enhanced. In order to gain some understanding of the physical processes involved in such an enhancement a comparison was made between thermal annealing and laser annealing of the implanted crystals. Clear differences were found in the cathodoluminescence spectra of the thermally annealed and laser-annealed samples. The increase in cathodoluminescence emission intensity produced by laser annealing was attributed to the production of selenium vacancies in the vicinity of the implanted erbium ions and leads us to suggest the possibility of site selective annealing by this technique.     

Multi-walled carbon nanotubes formed by condensed-phase conversions of Fe-C-based nanopowder in vacuum

We describe the formation of multi-walled carbon nanotubes (MWCNTs) which have grown during annealing at 800 °C of Fe-C-based nanopowder in vacuum. The Fe-C-based nanopowder was produced by a laser pyrolysis of gas-phase reactants. The as-synthesized and annealed samples were characterised by TEM, XRD, Mössbauer spectroscopy, Raman spectroscopy, and magnetic measurements. Under the TEM, MWCNTs were observed in the annealed sample. In addition, larger particles with the graphitic shells and various graphitic structures were found. XRD and Mössbauer analysis confirmed that only two iron phases were present in the annealed sample: α-Fe and Fe₃C. Phase transformations taking place during the thermal treatment of the sample are discussed.     

Low-temperature phase transformation of CZTS thin films

The low temperature phase transformation in the Cu_2ZnSnS_4(CZTS) films was investigated by laser annealing and low temperature thermal annealing.The Raman measurements show that a-high-power laser annealing could cause a red shift of the Raman scattering peaks of the kesterite(KS) structure and promotes the formation of the partially disordered kesterite(PD-KS) structure in the CZTS films,and the low-temperature thermal annealing only shifts the Raman scattering peak of KS phase by several wavenumber to low frequency and the broads Raman peaks in the low frequency region.Moreover,the above two processes were reversible.The Raman analyses of the CZTS samples prepared under different process show that the PD-KS structure tends to be found at low temperatures and low sulfur vapor pressures.Our results reveal that the control of the phase structure in CZTS films is feasible by adjusting the preparation process of the films.     

Fiber laser annealing of indium-tin-oxide nanoparticles for large area transparent conductive layers and optical film characterization

Indium tin oxide (ITO) coatings are widely used as transparent electrodes for optoelectronic devices. The most common preparation methods are sputtering, evaporation, and wet chemical deposition. ITO coatings can also be manufactured by solution deposition of ITO nanoparticles followed by furnace thermal annealing with the major motivation to reduce equipment investment. However, conventional furnace annealing is energy intensive, slow, and limited by the peak processing temperature. To overcome these constraints, we suggest using a laser beam for ITO nanoparticle annealing over a large area. It is shown in the present study that a low cost, high power, and high efficiency laser can yield large area functional ITO films in a process that carries substantial promise for potential industrial implementation. Furthermore, laser annealing generates higher electrical conductivity than conventional, thermally annealed nanoparticle films. The optical and electrical properties of the annealed ITO films can also be altered by adjusting laser parameters and environmental gases.     

Surface enhanced Raman scattering and photoluminescence properties of catalytic grown ZnO nanostructures

Sword-like (diameter ranging from 40 nm to 300 nm) and needle-like zinc oxide (ZnO) nanostructures (average tip diameter ∼40 nm) were synthesized on annealed silver template over silicon substrate and directly on silicon wafer, respectively via thermal evaporation of metallic zinc followed by a thermal annealing in air. The surface morphology, microstructure, chemical analysis and optical properties of the grown samples were investigated by field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, room temperature photoluminescence and Raman spectroscopy. The sword-like ZnO nanostructures grown on annealed silver template are of high optical quality compared to needle-like ZnO nanorods for UV emission and show enhanced Raman scattering.     

Crystallization of hydrogenated amorphous silicon carbon films with laser and thermal annealing

The crystallization of silicon rich hydrogenated amorphous silicon carbon films prepared by Plasma Enhanced Chemical Vapor Deposition technique has been induced by excimer laser annealing as well as thermal annealing. The excimer laser energy density (E_d) and the annealing temperature were varied from 123 to 242 mJ/cm² and from 250 to 1200 °C respectively. The effects of the two crystallization processes on the structural properties and bonding configurations of the films have been studied. The main results are that for the laser annealed samples, cubic SiC crystallites are formed for E_d ≥ 188 mJ/cm², while for the thermal annealed samples, micro-crystallites SiC and polycrystalline hexagonal SiC are observed for the annealing temperature of 800 and 1200 °C respectively. The crystallinity degree has been found to improve with the increase in the laser energy density as well as with the increase in the annealing temperature.     

CW CO2-laser annealing of arsenic implanted silicon

CW CO₂-laser annealing of arsenic implanted silicon was investigated in comparison with thermal annealing. Ion channeling, ellipsometry, and Hall effect measurements were performed to characterize the annealed layers and a correlation among the different methods was made. The laser annealing was done with power densities of 100 to 640 W cm⁻² for 1 to 20 s. It was found that the lattice disorder produced during implantation can be completely annealed out by laser annealing with a power density of 500 W cm⁻² and the arsenic atoms are brought on lattice sites up to 96±2%. The maximum sheet carrier concentration of 6×10¹⁵ cm⁻² was obtained for 1×10¹⁶ cm⁻² implantation after laser annealing, which was up to 33% higher than that after thermal annealing at 600 to 900°C for 30 min.     

GaAs/SiO_2超晶格的制备和Raman光谱研究

我们采用射频磁控溅射方法在 p- Si衬底上成功地制备出四周期的非晶 Ga As/Si O2超晶格 ,并取得其高分辨率电镜像。以 80 0℃快速退火方法使超晶格中非晶的 Ga As层局部晶化 ,利用 Raman散射谱研究了其结构变化。     

The effect of thermal annealing and laser irradiation on the microstructure of vanadium oxide nanotubes

The microstructure of vanadium oxide nanotubes (VONTs) have been characterized using FTIR spectroscopy and Raman spectroscopy. The temperature effects on the VONTs were studies by changing the laser irradiation power and thermal annealing temperature in air. Raman spectroscopy studies showed that the VONTs could be decomposed even at low laser power irradiation. Also, together with scanning electron microscopy, it was found that thermal annealing in air could lead to the collapse of the tubular structure and convert the nanotubes into V₂O₅ nanoparticle. It was found that the thermal stability of VONTs was relatively low and the tubular morphology was destroyed at temperatures higher than 300 °C. The spectroscopic analyses showed that the Raman signature of the VONTs could be established for probing tubular structure.     

Raman spectroscopy of sol–gel derived titanium oxide thin films

Raman spectra of TiO₂ films prepared via the sol–gel process were studied by UV and visible Raman spectroscopy. The evolution of the phases of TiO₂ films during annealing was investigated, and the relative intensities of the Raman bands excited with 325 nm were found to be distinct from those of the bands excited with 514 nm. The transmittance and FTIR spectra of the films annealed at different temperatures were characterized. The crystallization process of the powders and thin films treated by different annealing methods were also studied with Raman spectroscopy. The results show that the change in the relative intensities is caused by the resonance Raman effect. The anatase to rutile transition of the powder occurs at 700 °C, while that of the thin film occurs at 800 °C. The analysis of Raman band shape (peak position and full width at half‐maximum) after conventional furnace annealing and rapid thermal annealing indicates the influence of the non‐stoichiometry and phonon confinement effect. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman study of thermally annealed silicon small particles and thin films

A comparative study on thermal annealing of gas-evaporated silicon small particles and evaporated thin films is made using Raman scattering. The Raman spectra of the annealed silicon particles show only small change due to SiO bond on the surface, suggesting the crystalline structure of the particle. On the other hand, the films are crystallized thermally because of their amorphous-like nature; the activation energy of the crystallization can be determined by resolving the Raman spectra into crystalline parts and amorphous-like ones, and is found to be that of viscous flow (0.35 eV).     

Raman scattering in ion-implanted silicon exposed to rf-plasma treatment

The structural changes in implantation-amorphized silicon layers under radio-frequency (rf) discharge treatment, are studied by the Raman technique. The results are compared with those of thermally annealed samples. The rf treatment is shown to result in amorphous phase relaxation in silicon, while the thermal annealing converts a-Si into c-Si. The a-Si relaxation model under rf-plasma treatment is discussed.     

The effects of thermal annealing in self-assembled Ge/Si quantum dots

The effects of thermal annealing in Si base self-assembled Ge dots have been investigated by Raman spectra and PL spectra. An obvious Raman frequency shift under different annealing temperature can be observed. There are two main effects during the annealing procession: one is the inter-diffusion of the Si and Ge quantum dots; the other is the relaxation of the elastic strain. With the calculated results, PL blue shift can be related to strain relaxation effects, and/or a general decrease of Ge content due to the Ge-Si intermixing.     

快速热处理对应变InGaAs/GaAs单量子阱激光二极管电子发射和DX中心的影响

研究分子束外延(MBE)生长的应变In0.2Ga0.8AsGaAs折射率梯度变化异质结单量子阱激光二极管的快速热处理(RTA)效应.结果表明,RTA移除了InGaAsGaAs界面非辐射中心,提高77K光致发光效率和有源层电子发射.同时Al和Ga原子互扩散,也增加了AlGaAs波导层DX中心浓度.RTA处理后样品电流冲击老化实验证明DX中心浓度呈现出相应的增加.这表明DX中心可能是激光二极管性能退化的原因之一. 关键词： 量子阱 快速热处理 电子发射 DX中心     

Phosphorus diffusion and activation in fluorine co-implanted germanium after excimer laser annealing

The diffusion and the activation of phosphorus in phosphorus and fluorine co-implanted Ge after being annealed by excimer laser are investigated. The results prove that the fluorine element plays an important role in suppressing phosphorus diffusion and enhancing phosphorus activation. Moreover, the rapid thermal annealing process is utilized to evaluate and verify the role of fluorine element. During the initial annealing of co-implanted Ge, it is easier to form high bonding energy F_nV_m clusters which can stabilize the excess vacancies, resulting in the reduced vacancy-assisted diffusion of phosphorus. The maximum activation concentration of about 4.4×10²⁰ cm^-3 with a reduced diffusion length and dopant loss is achieved in co-implanted Ge that is annealed at a tailored laser fluence of 175 mJ/cm². The combination of excimer laser annealing and co-implantation technique provides a reference and guideline for high level n-type doping in Ge and is beneficial to its applications in the scaled Ge MOSFET technology and other devices.     

Enhanced infrared response of Si base p-n diode with self-assembled Ge quantum dots by thermal annealing

The effects of thermal annealing in Si base p-n diode with self-assembled Ge dots stacked in eight layers structure are investigated. The effects of annealing are discussed based on the photovoltage spectra, the PL spectra and the Raman spectra. Three main effects occur after thermal annealing: the reduction of point defects, the intermixing of Si-Ge and the strain relaxation. The experimental result shows that 800 °C might be a suitable annealing temperature for photovoltaic applications.     

Optical properties of laser-processed In x Ga1−x As

Various spots in GaAs, In-diffused with the 1.064 μm line of pulsed Nd:YAG laser with several energy densities, have been characterized and compared with samples prepared by the conventional rapid thermal annealing method. Of the energy densities used, the spot processed with an energy density of 7 J/cm² shows In _x Ga_1?x As phases with an indium concentration of 60% and below. An abrupt boundary in the indium concentration is observed at the edge of the laser-annealed spot. The diffusion depth is found to be less than 1000 Å. The spot processed with an energy density of 14 J/cm² shows considerable damage from the irradiation resulting in strain in the lattice. The samples prepared by the thermal annealing method show similar results to the laser-diffused samples. However, these thermally annealed samples suffer from arsenic loss unlike the laser-processed samples. It can be concluded that laser-induced alloying of indium into GaAs can be achieved with less arsenic loss than the thermal annealing method.