共查询到20条相似文献,搜索用时 15 毫秒
1.
H. M. Phillips D. Sarkar N. J. Halas R. H. Hauge R. Sauerbrey 《Applied Physics A: Materials Science & Processing》1993,57(1):105-107
The electrical conductivity of thin-film C60 has been changed by more than seven orders of magnitude with KrF (248nm) excimer-laser irradiation. Specific conductivities of 1 –1 · cm–1 have been obtained. The onset of conductivity is consistent with a laser-induced metal-insulator phase transition. The threshold for KrF-laser ablation of C60 has been determined to be 20±2 mJ/cm2. This laser-induced process generates an all-carbon semiconductor-metallic junction which may have important technological applications. 相似文献
2.
Weili Zhang Yiben XiaJianhua Ju Linjun WangZhijun Fang Minglong Zhang 《Solid State Communications》2003,126(3):163-166
The electrical conductivity of nitride carbon (DLC: N) films has been studied. It is found that the electrical conductivity of the deposited films increases slowly with increasing nitrogen content, however, it decreases after the nitrogen content in the film reaches a certain value of 12.8 at%. Thermal treatment results show that the electrical conductivity of the lowly nitrogen doped DLC film increases rapidly, while that of the heavily doped film decreases after annealing at 300 °C for 30 min. Raman and XPS spectra results show that when the nitrogen content in the films reaches a certain value, there appears nonconductive phases. Therefore the electrical conductivity of the heavily doped films decreases. FTIR spectra analysis results show that the nitrogen atom as an impurity center undergoes an ‘activation’ process during the thermal treatment, which leads to the increase of the electrical conductivity. Therefore, the nitrogen in these two kinds of films has different effects on the electrical conductivity. 相似文献
3.
R. Käsmaier S. Lätsch H. Hiraoka 《Applied Physics A: Materials Science & Processing》1996,63(4):305-313
A thin solid C60 film has been irradiated under a fix incident angle with pulsed UV light at the wavelength of 266 nm. With scanning electron microscopy and atomic force microscopy, a surface transformation of the irradiated films has been observed to a periodic surface structure at low laser fluences in air as well as in vacuum and to strong morphology changes at higher laser fluences only in air. For both structural transformations the occuring surface chemistry has been studied with Raman spectroscopy and X-ray photoelectron spectroscopy. In the case of the periodical lines, these results in addition to a detailed discussion of the existing models for laser induced surface structures have shown that the C60 film remains a van der Waals solid but with much oxygen incorporation in the lattice and does not polymerize as it is known to happen during continuous wave irradiation. The case of strong morphology changes could be explained by detailed comparison of the obtained Raman and X-ray photoelectron spectroscopy data as the formation of a new carbon phase with diamond-like sp3 bondings through an oxygen-assisted fullerene cage opening. 相似文献
4.
G. von Helden I. Holleman M. Putter G. Meijer 《Applied Physics A: Materials Science & Processing》1998,67(2):161-167
60 with trains of picosecond infrared (IR) pulses, tuned over the 8–15 μm range, is studied. At some specific wavelengths, white-light
emission as well as ejection of ionic species from the solid is observed. The spectral characteristics of the white-light
emission resemble those of a black body. The mass distribution of the ejected ionic species shows substantial amounts of C60 coalescence products. Unexpectedly, all these processes only occur at wavelengths where solid C60 is relatively transparent. No white-light emission nor ejection of ionic species is observed when being resonant with an
IR-allowed transition of C60. It is concluded that regular C60 is not the chromophore for the observed processes, and that sequential absorption of single photons by a strong absorber
that is dilute in the crystal takes place. Plausible chromophores are sites that are intercalated with alkali metals. Accumulation
of energy at these sites leads to fullerene coalescence in the solid, ion ejection, and white-light emission, ultimately resulting
in the destruction of the C60 molecules.
Received: 14 April 1998/Accepted: 22 April 1998 相似文献
5.
N. Grobert M. Terrones A.J. Osborne H. Terrones W.K. Hsu S. Trasobares Y.Q. Zhu J.P. Hare H.W. Kroto D.R.M. Walton 《Applied Physics A: Materials Science & Processing》1998,67(5):595-598
60 and Ni deposited on a silica plate at 950 °C. High-resolution transmission electron microscopy (HRTEM) studies reveal that
these tapered structures are almost completely filled with Ni and are closed at both ends. The diameters of the needles (2–5 μm
in length) range between 10–20 nm at one end and 30–200 nm at the other. A surprisingly high degree of graphitization is observed
in the walls of the nanotubes. These unique structures may prove useful as electrodes with various applications such as precision
probes in biological systems or scanning tunnelling microscope tips.
Received: 13 August 1998/Accepted: 13 August 1998 相似文献
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T. Feurer R. Sauerbrey M. C. Smayling B. J. Story 《Applied Physics A: Materials Science & Processing》1993,56(3):275-281
When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The conduction mechanism is phonon-assisted variable range hopping, evident from the observed temperature and electric field dependence of the resistivity at low conductivities. The laser-induced conductivity depends on the ambient atmosphere during irradiation. Transmission spectroscopy in the visible region and infrared Fourier transform spectroscopy have been used to characterize the material. A thermal mechanism is proposed for the formation of conducting polyimide, by excimer-laser irradiation. 相似文献
8.
A new transparent conducting oxide (TCO) film with low resistivity and high transmittance in the visible range, molybdenum-doped zinc oxide (MZO), was successfully prepared by RF magnetron sputtering method on glass substrates at room temperature. The structural, electrical, and optical properties as a function of film thickness were investigated. All the samples have a preferred orientation with the (0 0 2) planes parallel to the substrates. The resistivity initially decreases and then shows an increase with the increase of the film thickness. When the thickness is 400 nm, the film has its best crystallinity and lowest resistivity 9.2 × 10−4 Ω cm with a Hall mobility of 30 cm2 V−1 s−1 and a carrier concentration of 2.3 × 1020 cm−3. The average transmittance in the visible range exceeds 84% for all thickness films. 相似文献
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10.
S. Henke K. H. Thürer S. Geier B. Rauschenbach B. Stritzker 《Applied Physics A: Materials Science & Processing》1995,60(4):383-389
The growth of epitaxial C60 thin films on mica(001) by thermal evaporation has been studied in detail by X-ray pole-figure measurements. The influence of the deposition rate, the substrate temperature and the film thickness on the in-plane epitaxial arrangements and the formation of twins has been investigated. It has been demonstrated that the C60 growth is determined by two independent and equivalent C60-crystal grain alignments (type-A and type-B). The nearly six-fold symmetry of the mica(001)-substrate surface offers the three-fold fcc-(111)-oriented C60-crystal grains two equivalent crystal alignments. A high deposition rate of 0.5 Å/s is responsible for the formation of twins at a substrate temperature of 150°C, which diminishes by a higher substrate temperature of 200°C. By a decrease of the deposition rate down to 0.08 Å/s the twins vanish at a film thickness of 200 nm and at the substrate temperature of 150°C. Under the same sublimation conditions, in addition to the type-A and type-B crystal orientations, the growth of the thin C60 films starts with a slight fibre texture which does not appear at a larger film thickness. 相似文献
11.
Saleh T. Mahmoud H. Ghamlouche N. Qamhieh Hessa Al-Shamisi 《Applied Surface Science》2007,253(17):7242-7245
New preparation methods of electrical contacts have been developed to minimize their effect on Ge-Sb-Te thin films. Impedance spectroscopy technique has been used to extract the contributions of both electrical contacts and the material under investigation. Three different configurations of electrical contacts were investigated. The results show that the effect of the contacts disappears when silver paste is placed on the gold electrode only without touching and interacting with the Ge-Sb-Te film. 相似文献
12.
M. Ramm M. Ata T. Gross W. Unger 《Applied Physics A: Materials Science & Processing》2000,70(4):387-390
We report core-level and valence-band X-ray photoelectron spectroscopy (XPS) and carbon [
]K near-edge X-ray-absorptionfine structure spectroscopy (NEXAFS) results of plasma-polymerized C60. In comparison with evaporated C60 the C 1s peak is broader and asymmetric for the C60 polymer and its shake-up satellites diminished. Furthermore, the features of the valence-band as well as the features of
the π* antibonding orbitals of the C60 polymer are broader and reduced in intensity. Changes in the electronic structure are attributed to the polymerization of
C60, the post-plasma functionalization of the surface by oxygen after exposure to atmosphere, and the occurrence of amorphous
carbon.
Received: 28 May 1999 / Accepted: 31 August 1999 / Published online: 8 March 2000 相似文献
13.
The intrinsic and phosphorous (P)-doped hydrogenated amorphous silicon thin films were crystallized by laser annealing. The structural properties during crystallization process can be investigated. Observed redshifts of the Si Raman transverse optical phonon peak indicate tensile stress present in the films and become intense with the effect of doping, which can be relieved in P-doped films by introducing buffer layer structures. Based on experimental results, the established correlation between the stress and crystalline fraction (XC) suggests that the relatively high stress can limit the increase in XC and the highest crystalline fraction is obtained by a considerable stress release. At high laser energy density of 1250 mJ/cm2, the poorer crystalline quality and disordered structure of the film originating from the irradiation damage and defects lead to the low electron mobility. 相似文献
14.
To resolve the problem of p-type doping in ZnO, nitrogen and aluminum (N-Al) codoped ZnO films were prepared by the ultrasonic spray pyrolysis (USP) technique. The structural and electrical properties of N-Al codoped ZnO films were investigated. The results demonstrate that the undoped ZnO films exhibit the preferential orientation of (002) plane, while ZnO films show high orientation of (101) plane after codoping with N and Al. The N-Al codoped ZnO films under optimum conditions show p-type conduction, with a low resistivity of 1.7×10−2Ω cm, carrier concentration of 5.09×1018 cm−3 and high Hall mobility of 73.6 cm2 V−1 s−1. A conversion from p-type conduction to n-type was observed during the increase of measurement temperature. 相似文献
15.
Y. Shi C. M. Xiong X. S. Wang C. H. Lei H. X. Guo X. J. Fan 《Applied Physics A: Materials Science & Processing》1996,63(4):353-357
Polycrystalline C60 films are deposited onto a variety of substrates by ionized cluster beam deposition (ICBD) technique. The structure of the ICBD C60 films are studied by transmission electron microscopy (TEM). The electrical characteristics of the ICBD C60 films on silicon substrates are investigated by current-voltage (I–V) measurements. TheICBD C60/p-Si and C60/n-Si heterostructures show strong current rectification, which is analyzed using band theory. 相似文献
16.
T. L. Makarova V. G. Melekhin I. T. Serenkov V. I. Sakharov I. B. Zakharova V. É. Gasumyants 《Physics of the Solid State》2001,43(7):1393-1399
The structure, composition, and electrical and optical properties of thin tellurium-intercalated fullerene films C60Tex are investigated. The samples of compositions from C60Te0.1 to C60Te6 are prepared by thermal evaporation. The sample composition and the impurity distribution are controlled by the Rutherford backscattering technique. The Raman vibrational spectra indicate changes in the symmetry of a C60 molecule: the strain of the molecule increases with a decrease in the tellurium concentration and decreases as the tellurium impurity concentration increases. The evolution of the optical absorption spectra and the electrical conductivity suggests that intercalation of a tellurium impurity leads to modification of the electronic structure of the material. This process is accompanied by a shift and change in shape of the optical absorption edge and a change in the electrical conductivity of films by several orders of magnitude depending on the composition. The electrical conductivity is minimum at a low tellurium impurity content. 相似文献
17.
The ac electrical properties of metal-free phthalocyanine (H2PC) thin films have been studied in the frequency range from 102 to 2×104 Hz and in the temperature range from 150 to 475 K. The ac conductivity σ was found to vary as ωs with the index s≤1. Although these general values of s appear to be consistent with a hopping process, the present σ values
do not increase monotonically with temperature. At low frequency, the capacitance and loss tangent were found to be constant
over the entire frequency range, in good qualitative agreement with the equivalent circuit model consisting of an inherent
capacitance in parallel with a resistive element. Moreover, at constant frequency, the two parameters increased with increasing
temperature up to approximately 300 K. Above this temperature, another sharp decrease in both capacitance and loss tangent
was obtained. This type of behavior was interpreted in terms of nomadic (delocalized) polarization, which leads to an increase
in the dielectric constant. The drastic decrease of the capacitance and loss tangent observed above room temperature is thought
to be related to the decrease in the dielectric constant, which results from the inability of the domains to hold the increases
in free charge carrier concentration due to the increase of temperature.
Received: 6 December 2001 / Accepted: 7 January 2002 / Published online: 19 July 2002
RID="*"
ID="*"Corresponding author. Fax: +972-2/279-6960, E-mail: asaleh@science.alquds.edu 相似文献
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19.
M.E. Kozlov M. Tokumoto K. Yakushi 《Applied Physics A: Materials Science & Processing》1997,64(3):241-245
60 are reported. The material associated with the mixture of rhombohedral and tetragonal phases was synthesized under pressure
of when treatment temperature was only a little lower than the high-temperature limit of C60 stability. The substance exhibits very rich infrared and Raman spectra as well as luminescence spectra of an unusual shape.
They show that vibrational transitions in the prepared carbon architecture substantially deviate from icosahedral symmetry
of buckyballs and exhibit a similarity with lattice phonons in graphite. It may originate from mixing of C60 modes and vibrations of a layer structure on deformed and weakly bound fullerene molecules. The luminescence spectra reveal
three distinct electronic states located below . One of them responsible for the emission peak at is very characteristic for the pressure modified fullerene. The data should be useful for the accurate determination of structural
changes in C60 induced by pressure.
Received: 6 September 1996/Accepted: 10 October 1996 相似文献
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