共查询到20条相似文献,搜索用时 46 毫秒
1.
K. Narumi Y. Xu K. Miyashita H. Naramoto 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):385-388
We report a new effect of ion irradiation on
C60 thin films:
C60 thin films irradiated with 7-MeV
C2+ ions show resistance to
photopolymerization. The resistance increases with increasing
ion fluence of irradiation. The effect is qualitatively
explained by the fact that the number of a
C60 pair satisfying the topochemical
requirement for photochemical reaction in solids decreases by
destruction of C60 molecules accompanied
by lattice disorder. 相似文献
2.
金属多层膜调制周期下降到纳米级时,其力学性质会发生显著改变. Cu-Ni晶格失配度约为2.7%,可以形成共格界面和半共格界面,实验中实现沿[111]方向生长的调制周期为几纳米且具有异孪晶界面结构的Cu/Ni多层膜,其力学性质发生显著改变.本文采用分子动力学方法对共格界面、共格孪晶界面、半共格界面、半共格孪晶界面等四种不同界面结构的Cu/Ni多层膜进行纳米压痕模拟,研究压痕过程中不同界面结构类型的形变演化规律以及位错与界面的相互作用,获取Cu/Ni多层膜不同界面结构对其力学性能的影响特征.计算结果表明,不同界面结构的样品在不同压痕深度时表现出的强化或软化作用机理不同,软化机制主要是由于形成了平行于界面的分位错以及孪晶界面的迁移,强化机制主要是由于界面对位错的限定作用以及失配位错网状结构与孪晶界面迁移时所形成的弓形位错之间的相互作用. 相似文献
3.
A crystal-to-amorphous structural transition was induced in the Ni25W75 and Ni35W65 multilayers by ion irradiation at room temperature. More interestingly, prior to complete amorphization, a sequential disordering
of first Ni and then W crystalline lattices was observed in the Ni25W75 sample with increasing ion dose. Such sequence in disordering is attributed to the difference in melting points between the
two constituent metals. In another two multilayered samples with overall compositions of Ni60W40 and Ni78Nb22, ion irradiation under similar conditions resulted in the formation of two Ni-based fcc solid solutions, respectively. In
comparison, the same Ni-based fcc solid solution was formed in the Ni35W65 multilayered sample upon solid-state reaction at 500 °C. Solid-state reaction at 550 °C resulted in the formation of a new
W-rich metastable hcp phase in the Ni25W75 multilayered sample and the bcc–hcp transition was thought to be realized through a shearing mechanism. A Gibbs free-energy
diagram, including the free-energy curves of the newly formed metastable crystalline phases, of the Ni-W system was calculated
based on Miedema’s model and it can give a reasonable explanation of the observed sequential disordering. The calculated results
also showed that the free-energy difference between the amorphous and metastable crystalline phases was quite small, leading
to a situation that the phase selection, namely which phase was more favored to be formed eventually than its competitors,
was influenced or even determined by the kinetics involved in the respective processes. Besides, the growth kinetics of the
MX phases was also discussed.
Received: 26 January 1999 / Accepted: 8 March 1999 / Published online: 14 June 1999 相似文献
4.
R. V. Kumar 《Ionics》1999,5(3-4):194-199
It is conceivable that sophisticated sensing and other electrochemical devices can be formed by interfacing more than one
solid electrolyte in an electrochemical chain involving more complicated sequences of electrodes, interfaces, in-situ catalysts
and semi-permeable membranes. As sensor systems become more elaborate, the need for optimising several interfaces and reaction
equilibria becomes critical.
In the example of YSZ/Nasicon based sensors, the emf response can be adequately explained by the interfacial reactions. In
the use of doped perovskite interfaced with an oxygen or a chloride ion conductor, although useful sensors can be devised
with Nernstian type of response, the interfacial phenomena or the electrode reactions are more complicated and can not be
explained by simple interfacial reactions. A brief review of the relevant concepts is presented.
Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. 相似文献
5.
This paper reports changes in refractive index and thickness of spin-coated poly(methyl methacrylate) (PMMA) thin films upon irradiation by a conventional high-pressure mercury UV lamp. Significant increase in refractive index and reduction in thickness are detected. Index modulations of greater than 0.01 are achieved in the thin films after 4 min of irradiation. The thickness reduction of an irradiated PMMA film is consistent with its weight loss. This is caused by the escape of the volatile molecules generated during the irradiation process. A slight increase in the refractive index is also found in the film, heat-treated above its glass transition temperature (Tg). This thermal effect is detected in the UV irradiation process. We propose three possible aliphatic structures that are formed during the photochemical reaction and may exist in the main chain of irradiated PMMA after the irradiation. Their refractive indices in aggregate state are greater than that of PMMA based on an evaluation using the Lorentz-Lorenz equation. This is suggested to be an important reason for the refractive index increase in the UV-irradiated PMMA films. A UV-irradiated film, heat-treated above its Tg, has a rough surface with many tiny holes as illustrated by atomic force microscopy. These holes are attributed to the evaporation of the small molecules generated during the irradiation process. 相似文献
6.
Tadashi Suzuki Takao Miyazaki Nobuyoshi Natsuaki 《Applied Physics A: Materials Science & Processing》1990,50(3):265-267
The origin of the ion beam mixing effect, which causes the formation of smooth silicide films, is investigated for the Ti/Si solid-phase silicidation reaction. Ge ion beam mixing of a conventional Ti/c-Si structure with an oxide-contaminated interface shows an obvious effect when the implant conditions are such that the Ti/Si interface is amorphized. On the other hand, silicidation without ion mixing for Ti/a-Si and Ti/c-Si structures with oxide-free interfaces, prepared by sequential deposition in UHV, results in smooth and rough film surfaces, respectively. This strongly suggests that the ion beam mixing effect primarily comes from the amorphization of the Si substrate surface rather than the destruction of the interfacial oxide film. 相似文献
7.
Q. Zhang W.S. Lai G.W. Yang B.X. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):223-231
An embedded-atom potential for the Ni-Nb system is constructed using physical properties obtained from first-principle calculations.
Employing the potential, molecular-dynamics simulations are performed to study the interfacial reaction in Ni/Nb multilayers
upon annealing at medium temperatures. The results show that a preset disordered interlayer, which is obtained by exchanging
Ni and Nb atoms in the interfaces, may act as a nucleus of amorphous phase and is usually necessary for amorphization. It
is found that the growth of the amorphous interlayer is in a planar mode and exhibits an asymmetric behavior due to a faster
consumption of Ni than that of the Nb layer; this is also indeed observed experimentally. Moreover, performing a simulation
with solid solution models, it is found that the Nb lattice can accommodate a large number of Ni atoms and still retain a
crystalline structure, while a small amount of Nb atoms induce a spontaneous decay of the Ni lattice. Such differences in
solid solubility is thought to be the physical origin of the asymmetric growth observed in experiments and simulations.
Received 7 June 1999 and Received in final form 12 January 2000 相似文献
8.
Y.F. Lu S.M. Huang C.H.A. Huan X.F. Luo 《Applied Physics A: Materials Science & Processing》1999,68(6):647-651
It is demonstrated that a liquid hydrocarbon precursor, cyclohexane, is appropriate for laser-induced carbon deposition. Amorphous
hydrogenated carbon films (a-C:H) were deposited by KrF excimer laser irradiation of single-crystal silicon surface immersed
under cyclohexane. The technique is simple and easy to operate. IR absorption spectra of the deposited films confirmed the
presence of carbon in the diamond phase. Raman and XPS studies showed diamond-like character of the deposited films. Moreover,
these two studies provided strong evidence that laser fluence played an important role in the formation of DLC bondings and
the quality of the deposited films.
Received: 15 September 1998 / Accepted: 5 January 1999 / Published online: 5 May 1999 相似文献
9.
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
10.
We present observations of sub-micron- to micron-sized particles generated by high fluence (≈2 J/cm2) 248-nm laser ablation of pressed polytetrafluorethylene (PTFE) targets in air at atmospheric pressure. The original target
material was hydrostatically compressed ≈7 μm PTFE powder, sintered at 275 °C. Collected ejecta due to laser irradiation consists
of four basic particle morphologies ranging from small particles 50–200 nm in diameter to larger particles ≈10 μm in diameter.
Many particles formed in air carry electric charge. Using charged electrodes we are able to collect charged particles to determine
relative numbers of ± charge. We observe roughly equal numbers of positively and negatively charged particles except for the
largest particles which were predominantly negative. For a range of particle sizes we are able to measure the sign and magnitude
of this charge with a Millikan-oil-drop technique and determine surface charge densities. The implications of these observations
with respect to pulsed laser deposition of PTFE thin films and coatings are discussed.
Received: 15 January 1999 / Accepted: 18 January 1999 / Published online: 7 April 1999 相似文献
11.
A X-ray photoelectron spectroscopy (XPS) study of the behaviour of sodium films deposited in ultra-high vacuum on InSe single-crystal or thin epitaxial films at room temperature and upon moderate annealings (up to 475 K) is reported. Major changes affect the substrate spectra, in particular indium, and clearly show the influence of the substrate morphology. For the InSe single-crystal substrate, annealing tends to restore the initial InSe surface as shown by XPS and RHEED, while for InSe films, no restoration occurs. In both cases, sodium has a partial ionic character and two phases are evidenced: one, [NaIn0Seβ], where indium is close to metal or covalent indium, and the other, Na'[InSe], where indium is more ionic close to InSe. The results emphasize that interdiffusion and fast chemical reaction predominate for the thin film substrate; for the bulk substrate, interfacial reaction and surface diffusion are competitive. 相似文献
12.
S. Chandramohan R. Sathyamoorthy P. Sudhagar D. Kanjilal D. Kabiraj K. Asokan V. Ganesan T. Shripathi U. P. Deshpande 《Applied Physics A: Materials Science & Processing》2009,94(3):703-714
The effect of high electronic energy deposition on the structure, surface topography, optical properties, and electronic structure
of cadmium sulfide (CdS) thin films have been investigated by irradiating the films with 100 MeV Ag+7 ions at different ion fluences in the range of 1012–1013 ions/cm2. The CdS films were deposited on glass substrate by thermal evaporation, and the films studied in the present work are polycrystalline
with crystallites preferentially oriented along (002)-H direction. It is shown that swift heavy ion (SHI) irradiation leads
to grain agglomeration and hence an increase in the grain size at low ion fluences. The observed lattice compaction was related
to irradiation induced polygonization. The optical band gap energy decreased after irradiation, possibly due to the combined
effect of change in the grain size and in the creation of intermediate energy levels. Enhanced nonradiative recombination
via additional deep levels, introduced by SHI irradiation was noticed from photoluminescence (PL) analysis. A shift in the
core levels associated with the change in Fermi level position was realized from XPS analysis. The chemistry of CdS film surface
was studied which showed profound chemisorption of oxygen on the surface of CdS. 相似文献
13.
Swift heavy ion (SHI) irradiation is an effective technique to modify the optical properties of the materials. In the present investigation, the effect of 100?MeV?Ag7+ SHI irradiation fluence on the optical properties of ZnO1?x:Nx thin films was studied. The post irradiation spectroscopic characterizations such as UV–VIS reflectance spectroscopy, Raman spectroscopy and photoluminescence (PL) spectroscopy analysis were carried out. The studies imply that when the SHI passes through the solid, the higher electronic stopping power of ions can weaken oxygen bonds in ZnO, resulting in the formation of donor defects such as oxygen vacancies and zinc interstitials. The formation of donor defects has been acknowledged through the increase in bandgap with irradiating ion fluence. The blue shift observed from the Raman spectra for the 3?×?1013 ions/cm2 fluence-irradiated films implies the existence of compressive stress in the films. The PL analysis acknowledges the formation of donor defects upon irradiation. Furthermore, it conveys that the presence of N atoms in ZnO lattice leads to the formation of a less number of defects as compared with undoped ZnO while irradiation. 相似文献
14.
Hydrophobic properties of thin nanostructured silver films produced by galvanic exchange reaction on a copper surface were studied after passivation with stearic acid. The morphology of the silver films was controlled by varying the concentration of silver nitrate in the solution. Water contact angle as high as 156° and contact angle hysteresis as low as 5° were achieved for samples obtained with initial silver ion concentration of 24.75 mM in the solution. However, a strong dependence of contact angle and contact angle hysteresis on the fractal-like morphology of the silver films was observed with the variation of silver ion concentration. 相似文献
15.
a-SiNx:H thin films of different stoichiometry grown by PECVD were subjected to irradiation by 100 MeV Au8+ ions with various fluences to understand the effect of stoichiometry on properties of thin films upon irradiation. Ellipsometry and UV–Vis study suggest the variation in the refractive index of thin films with fluence. The evolution of Hydrogen due to irradiation is quantified with the help of ERDA. RBS was probed to study the change in thin films' composition upon irradiation, which further helps understand the change in thin films' optical properties. Quenching of photoluminescence in the films with all stoichiometries was also observed due to ion irradiation. X-TEM images show the formation of discontinuous ion tracks of radius 2.5 nm in the film closer to silicon nitride stoichiometry. However, Si rich film does not show the clear formation of tracks. Results are explained in the framework of the Thermal spike mechanism of ion-solid interaction. 相似文献
16.
F. Beinhorn J. Ihlemann K. Luther J. Troe 《Applied Physics A: Materials Science & Processing》1999,68(6):709-713
Micro-lenses with well-defined optical parameters are generated on polymethylmethacrylate (PMMA) substrates doped with diphenyltriazene
(DPT) by controlled use of a swelling effect generated under conditions of subablative excimer laser illumination. The surface
profiles depend on the laser spot size and energy density. A sensitively balanced combination of matrix softening, substrate
volume expansion due to photochemical nitrogen release, and surface tension is responsible for the final shape of the lenses.
Complete arrays of identical lenses with 15 μm diameters and a focal length of 30 μm are produced by irradiation of (0.25 wt. %)
DPT-PMMA with a single laser pulse at a wavelength of 308 nm and a fluence of 3 J/cm2. It is shown experimentally and theoretically that appropriate volume expansion is possible without introducing internal
light scattering due to the formation of small bubbles.
Received: 7 April 1999 / Accepted: 8 April 1999 / Published online: 5 May 1999 相似文献
17.
F. Machalett K. Edinger J. Melngailis M. Diegel K. Steenbeck E. Steinbeiss 《Applied Physics A: Materials Science & Processing》2000,71(3):331-335
For direct writing of electrically conducting connections and areas into insulating gold oxide thin films a scanning Ar+ laser beam and a 30 keV Ga+ focused ion beam (FIB) have been used. The gold oxide films are prepared by magnetron sputtering under argon/oxygen plasma.
The patterning of larger areas (dimension 10–100 μm) has been carried out with the laser beam by local heating of the selected
area above the decomposition temperature of AuOx (130–150 °C). For smaller dimensions (100 nm to 10 μm) the FIB irradiation could be used. With both complementary methods
a reduction of the sheet resistance by 6–7 orders of magnitude has been achieved in the irradiated regions (e.g. with FIB
irradiation from 1.5×107 Ω/□ to approximately 6 Ω/□). The energy-dispersive X-ray analysis (EDX) show a considerably reduced oxygen content in the
irradiated areas, and scanning electron microscopy (SEM), as well as atomic force microscopy (AFM) investigations, indicate
that the FIB patterning in the low-dose region (1014 Ga+/cm2) is combined with a volume reduction, which is caused by oxygen escape rather than by sputtering.
Received: 30 May 2000 / Accepted: 31 May 2000 / Published online: 13 July 2000 相似文献
18.
M. Waiblinger Ch. Sommerhalter B. Pietzak J. Krauser B. Mertesacker M.Ch. Lux-Steiner S. Klaumünzer A. Weidinger C. Ronning H. Hofsäß 《Applied Physics A: Materials Science & Processing》1999,69(2):239-240
Electrically conducting channels in an insulating carbon matrix were produced by 140-MeV Xe ion irradiation. The high local
energy deposition of the individual ions along their pathes causes a rearrangement of the carbon atoms and leads to a transformation
of the insulating, diamond-like (sp3-bonding) form of carbon into the conducting, graphitic (sp2-bonding) configuration. The conducting ion tracks are clearly seen in the current mapping performed with an atomic force
microscope (AFM). These conducting tracks are of possible use in field emission applications.
Received: 4 May 1999 / Accepted: 5 May 1999 / Published online: 1 July 1999 相似文献
19.
M. Andersson A. Iline F. Stietz F. Träger 《Applied Physics A: Materials Science & Processing》1999,68(5):609-614
Gold films with a nominal thickness of 5–40 monolayers were grown on dielectric substrates and imaged by scanning force microscopy
(SFM). The films originally consisted of well-separated or densely packed clusters. During imaging in contact mode, the morphology
of the films changed drastically. At low coverage, i.e. Θ<10 monolayers, the well-known stripes originating from mobile clusters,
eventually accumulated into larger aggregates, were observed. In contrast, at larger coverage, highly ordered structures consisting
of one-dimensional wires evolved during scanning. They often were parallel with equal separation, i.e. well-defined periodicity,
over distances of several μm. Typically, the wires were 5–10 nm high and 50–100 nm wide. Investigations of Au films prepared
at varying temperature on different dielectric substrates allow us to suggest a self-assembling mechanism for wire formation
in which gold is periodically collected by the SFM tip and redeposited as soon as a critical amount is reached.
Received: 22 February 1999 / Accepted: 2 March 1999 / Published online: 7 April 1999 相似文献
20.
R. Mantovan C. Wiemer A. Zenkevich M. Fanciulli 《Journal of magnetism and magnetic materials》2009,321(15):2350-2353
The interfaces between ferromagnetic electrodes and tunnel oxides play a crucial role in determining the performances of spin-based electronic devices, such as magnetic tunnel junctions. Therefore, a deep knowledge of the structural, chemical, and magnetic properties of the buried interfaces is required. We study the influence of rapid thermal annealing treatments up to 500 °C on the interfacial properties of the Fe/Lu2O3 system. As-grown stacks reveal the presence of hydrogenated Fe-Lu-H intermetallic phases at the Fe/Lu2O3 interface most likely due to the H absorption on the Lu2O3 surface upon exposure to air and/or to the oxide growth. The annealing treatments induce remarkable changes of the structural, chemical, and magnetic properties at the interface, as evidenced at the atomic scale by the sub-monolayer sensitivity of conversion electron Mössbauer spectroscopy. The use of complementary techniques such as X-ray diffraction, time-of-flight secondary ion mass spectrometry, and in situ X-ray photoelectron spectroscopy, confirms that the main effect of the annealing is to gradually promote the dehydrogenation at the Fe/Lu2O3 interface. 相似文献