共查询到20条相似文献,搜索用时 15 毫秒
1.
R. Serna C. N. Afonso A. K. Petford-Long N. J. Long 《Applied Physics A: Materials Science & Processing》1993,56(2):132-137
The onset of mixing at the interfaces between Sb and Ge in thin multilayered films containing two or four layers has been studied. The films were irradiated with nanosecond laser pulses in order to trigger mixing, and in situ reflectivity measurements were used to follow the transformation in real-time. Cross sectional transmission electron microscopy analysis was used to study both the structure and the composition profile before and after irradiation.A threshold irradiation energy exists for the onset of mixing, below which roughening of the interface between the layers is observed, together with recrystallization of the surface Sb layer following melting. The results are consistent with a melting/diffusion process which is inhomogeneously nucleated at the interface between the top Sb and Ge layers. Once mixing is initiated an amorphous Sb-Ge layer of constant thickness is formed, corresponding to mixing along a well defined planar melt front. Voids are observed at the former Sb/Ge interface, which may be related to interfacial stress in the as-grown configuration. 相似文献
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Crystallization is induced by pulsed laser irradiation of s-deposited amorphous Ge2Sb2Te5 films. Changes of the irradiated areas have been analyzed with the reflectivity contrast. As laser fluences increasing,the reflectivity contrast increases from 0% - 2% to 14% - 16%, which indicates the structure of as deposited films transforms from amorphous to crystalline phases. The process of crystallization driven by the movement and rearrangement of atoms is described. And also the influence of the pulse duration on the threshold of crystallization is discussed, the results show that a lower threshold of crystallization can be produced for as-deposited films irradiated by the laser with short pulse duration. However, by the laser with long pulse duration, crystallization can only be formed with a higher threshold. The crystallization of films by irradiation of laser pulses is studied by Raman spectra. 相似文献
4.
N. Starbov T. Missana C. N. Afonso K. Starbova M. A. Ollacarizqueta 《Applied Physics A: Materials Science & Processing》1996,63(2):161-165
Bilayer Sb/Se films are irradiated with 12 ns pulses from an ArF laser (extended areas) and from a focused Ar+ laser (micron-sized areas). Real-time reflectivity measurements are used to determine if the process occurs within the solid or liquid phase and the transformation time, in addition to measure the optical contrast and the medium sensitivity. Transmission electron microscopy is used to analyze the structure of the transformed areas and the medium resolution. The results show that mixing is initiated by preferential melting at the grain boundaries and an amorphous phase is produced upon irradiation at high energy densities. Finally, the characteristics of the mixing process in Sb/Se films as a write-once optical recording mechanism are discussed in terms of the sensitivity and resolution of the recorded spots and the time required for recording. 相似文献
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OpticalRecordingPerformanceofIn_(47)Sb_(14)Te_(39)PhaseChangeThinFilmsusing514.5nmWavelengthLaserBeam¥MENLiqiu;JIANGFusong;GAN?.. 相似文献
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The process of oxide removal in crystalline Ge using a pulsed ultraviolet laser has been studied by means of real-time reflectivity measurements with nanosecond resolution. The interaction of laser radiation with a clean, oxide-free surface has been characterized and the inhomogeneous and homogeneous energy density melting thresholds of c-Ge for 193 nm radiation have been determined. The values are 180 and 370 mJ/cm2, respectively. We have demonstrated that it is possible to remove an oxide overlayer by irradiation in vacuum and to produce a surface that shows the same response to laser radiation as a smooth, oxide-free, chemically cleaned surface. Under certain specific irradiation conditions it is even possible, after removing the oxide overlayer, to produce an enhanced crystalline quality in the near-surface region compared to that obtained upon chemical cleaning as evidenced by Rutherford backscattering/channeling measurements. 相似文献
7.
T. Missana C. N. Afonso M. F. da Silva 《Applied Physics A: Materials Science & Processing》1994,59(6):653-658
Interdiffusion processes are induced by nanosecond laser pulses from an excimer laser. The Bi-based systems studied are formed by a Bi layer and a Sb or Ge layer. Configurations with Bi at the surface layer or at the innermost layer are both studied. Real-time reflectivity measurements are performed during the irradiation to determine the process kinetics and times and Rutherford backscattering spectrometry is used to obtain the concentration depth profiles. It will be shown that there is an interfacially initiated diffusion process in the Bi-Sb system and that the diffusion coefficients of this system within the liquid phase are in the 10–5–10–6 cm2/s range. The Bi-Ge system shows instead little mixing, the diffusion coefficients of the system within the liquid phase being at least two orders of magnitude lower. The differences observed when Bi is the surface layer or the innermost one are related to the different thermal responses of the system. 相似文献
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利用双光束反射率测量装置,研究了连续激光重复加载作用下30CrMnSiA钢金属材料的反射率变化特性。通过激光加载、冷却然后再加载到更高的温度的辐照试验与激光单次辐照的结果比较,发现二次加载时材料表面的激光反射率与样品表面首次加载时达到的最高温度所对应的反射率基本一致,只有达到并超过首次加载时样品曾达到的最高温度后,样品表面的反射率才会再次发生变化,且变化趋势与单次完整加载时的路径重合。这表明样品表面的反射率与其达到的最高温度有关,进一步的研究结果表明,样品达到的最高温度与样品表面在最高温度下产生的氧化反应层有关,而这一氧化层在冷却过程和再加载过程不变化。 相似文献
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R. Serna C. N. Afonso A. K. Petford-Long N. J. Long 《Applied Physics A: Materials Science & Processing》1994,58(2):197-202
Thin multilayer films (Ge/Sb/Ge/Sb/Si substrate) have been irradiated with single nanosecond laser pulses (=193 nm). Real-Time Reflectivity (RTR) measurements have been used to follow the transformation in situ and cross-sectional transmission electron microscope analysis was used to study both the microstructure and the composition profile before and after irradiation. Melting and mixing are both found to nucleate at preferential sites in the upper Ge/Sb interface. During this process the film surface topography changes in a way not previously seen, and rippling of the film is observed due to lateral mass flow induced in the Sb layer underneath the surface, most probably arising from volume changes upon melting. For the highest irradiation energy densities, melting of the whole multilayer configuration takes place, the ripples are no longer observed, and following cooling and solidification, a mixed amorphous GeSb film is formed. 相似文献
10.
F. Vega R. Serna J. Solís C. N. Afonso 《Applied Physics A: Materials Science & Processing》1994,58(4):417-421
Laser-induced oxidation of single-crystalline antimony and polycrystalline Sb films is studied. The samples are irradiated in an oxygen atmosphere (1.2 bar) by means of UltraViolet (UV) laser pulses while reflectivity measurements are used to monitor the oxidation process in real time. It is shown that there is an optical coupling between the growing oxide layer and the bulk material underneath which produces a dynamical change of the optical properties and leads to a non-constant growth rate. Depending on the laser energy density used, there is a critical oxide thickness above which a material-loss process starts, limiting the ultimate growth of the oxide layer. 相似文献
11.
The femtosecond-laser in situ keratomileusis procedure affords the opportunity to correct ametropia by cutting transparent
corneal tissue with ultra-short laser pulses. Thereby the tissue cut is generated by a laser-induced optical breakdown in
the cornea with ultra-short laser pulses in the near-infrared range. Compared to standard procedures such as photorefractive
keratectomy and laser in-situ keratomileusis with the excimer laser, where the risk potential for the eye is low due to the
complete absorption of ultraviolet irradiation from corneal tissue, only a certain amount of the pulse energy is deposited
in the cornea during the fs-LASIK process. The remaining energy propagates through the eye and interacts with the retina and
the strong absorbing tissue layers behind. The objective of the presented study was to determine and compare the retina damage
thresholds during the fs-LASIK process simulated with two various laser systems in the CW- and fs-regime. 相似文献
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Traian Dascalu Sofia E Acosta-Ortiz Martin Ortiz-Morales Isaac Compean 《Optics and Lasers in Engineering》2000,34(3)
Our experiments show that the laser fading process removes efficiently indigo-dye from denim support. We use the beams from Nd : YAG laser (1064 nm and its second harmonic 532 nm) and CO2 (10.6 μm) lasers. Different laser pulse parameters were used in order to obtain laser power density and fluency to start the ablation process. The purpose of this work is to determine the change of denim diffuse reflectivity spectra after laser irradiation with different wavelength and different power density. The change of diffuse reflectivity coefficient was up to 17% at 450 nm wavelength (from 8% reflectivity for unirradiated denim). 相似文献
14.
Laser-induced transformations (optical and compositional) of amorphousMO
x
thin films are studied as a function of the oxygen content and the nature of theM element,M being either a semiconductor (Ge) or a semi-metal (Sb). A high optical contrast in reflectivity is always found associated to the first laser pulses, this process being unaffected by the presence of oxygen. Next pulses lead to a process which may involve optical changes depending on the environmental conditions. Whereas the former optical changes are most likely related to a structural process which is completed before oxidation starts, the latter ones occur when irradiating at high oxygen pressures (1.2 bar) and thus they are easily related to an oxidation process. At low oxygen pressures (close to the oxygen partial pressure in air), the films show a good compositional stability upon irradiation together with a high optical contrast. 相似文献
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建立了描述噪声起振和Stokes种子光辅助起振的SBS(受激布里渊散射)理论模型,利用变步长有限差分方法数值求解了一维瞬态后向SBS耦合波方程组,得到了抽运光和散射光光强以及介质密度变化量的时空分布;研究了Stokes激光场对SBS反射率以及发生阈值的影响,发现Stokes种子光的存在大大减短了SBS过程的起振时间,并且在抽运光脉冲宽度固定的情况下使SBS的发生阈值大幅度降低;最后,探讨了瞬态受激布里渊过程对光学材料破坏的可能性并对今后的工作进行了展望.
关键词:
光学透明材料
受激布里渊散射
斯托克斯种子光
反射率 相似文献
17.
G. Račiukaitis S. Grubinskas P. Gečys M. Gedvilas 《Applied Physics A: Materials Science & Processing》2013,110(1):93-98
Selectiveness of the laser processing is the top-most important for applications of the processing technology in thin-film electronics, including photovoltaics. Coupling of laser energy in multilayered thin-film structures, depending on photo-physical properties of the layers and laser wavelength was investigated experimentally and theoretically. Energy coupling within thin films highly depends on the film structure. The finite element and two-temperature models were applied to simulate the energy and temperature distributions inside the stack of different layers of a thin-film solar cell during a picosecond laser irradiation. Reaction of the films to the laser irradiation was conditioned by optical properties of the layers at the wavelength of laser radiation. Simulation results are consistent with the experimental data achieved in laser scribing of copper-indium-gallium diselenide (CIGS) solar cells on a flexible polymer substrate using picosecond-pulsed lasers. Selection of the right laser wavelength (1064 nm or 1572 nm) enabled keeping the energy coupling in a well-defined volume at the interlayer interface. High absorption at inner interface of the layers triggered localized temperature increase. Transient stress caused by the rapid temperature rise facilitating peeling of the films rather than evaporation. Ultra-short pulses ensured high energy input rate into absorbing material permitting peeling of the layers with no influence on the remaining material. 相似文献
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Tomas Grinys Mantas Dmukauskas Mindaugas Ščiuka Saulius Nargelas Andrius Melninkaitis 《Applied Physics A: Materials Science & Processing》2014,114(2):381-385
Mg- and Si-doped GaN layers deposited by metalorganic chemical vapor deposition method were irradiated with femtosecond pulse duration laser of three different wavelengths 1,030, 515 and 343 nm. Both single and multiple shot laser induced damage thresholds of doped GaN layers were evaluated and discussed. The scanning electron microscopy employed with electron beam induced current and energy dispersive X-ray techniques were used to study laser damage morphology. It was observed that ablated area and laser-induced damage increased with irradiation fluence. The mechanism of damage generation by Gaussian beam profile laser was considered. 相似文献
19.
R. I. Batalov R. M. Bayazitov D. I. Kryzhkov P. I. Gajduk E. I. Gatskevich G. D. Ivlev C. P. Marques E. Alves 《Journal of Applied Spectroscopy》2009,76(2):209-214
The dynamics of phase transitions induced by nanopulsed ruby laser radiation (80 nsec, 2 J/cm2) both in silicon layers doped with erbium ions and in those containing doped erbium and oxygen have been studied by an optical
probing method. It is shown that the reflectivity behavior of structures under pulsed irradiation is governed by phase transitions
(melting and crystallization) of implanted silicon and also by interference effects at the interfaces of the resulting phases.
It is established that the profiles of erbium distribution change under nanosecond laser irradiation and that the dopant is
forced out to the surface due to a segregation effect at small implantation doses. As the implanatation dose increases, diffusion
deep into the sample tends to prevail over segregation. A considerable increase in the photoluminescence peak intensity at
0.81 eV is found after both the pulsed laser processing and thermal post-annealing of doped samples as opposed to spectra
of samples subjected either to thermal annealing or to pulsed laser irradiation.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 225–231, March–April, 2009. 相似文献
20.
Ultrafast thermomechanical responses of silicon thin films due to ultrashort-pulsed laser irradiation were investigated using
an atomic-level hybrid method coupling the molecular dynamics and the ultrafast two-step energy transport model. The dynamic
reflectivity and absorption were considered, and the effects of laser fluence and pulse duration on the thermomechanical response
were studied. It was found that both the carrier temperature and number density rapidly increase to their maximum while the
lattice temperature rises at a much slower rate. The ultrafast laser heating could induce a strong stress wave in the film,
with the maximum compressive and tensile stress occurring near the front and back surfaces, respectively. For laser pulses
of the same duration, the higher the laser fluence is, the higher the carrier temperature and density and lattice temperature
are induced. For the same laser fluence, a longer pulse generally produces lower carrier density and temperatures and weaker
stress shock strength. However, for the fluence of 0.2 J/cm2, the lowest lattice temperature was simulated for a 100-fs pulse compared to the 1-ps and 5-ps pulses, due to the increase
of reflectivity by high carrier density. It is also shown that the optical properties as functions of lattice temperature
usually employed are not suited for modeling ultrafast laser interactions with silicon materials. 相似文献