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1.
Compatible with existing processing technology, chemical vapor deposition method is used to synthesize ZrS2 and HfS2 films a a large scale. The nonlinear optical properties are characterized by Z-scan measurement with femtosecond pulses at 800 nm. The results show that saturable absorption happens in ZrS2 owing to the larger ground state absorption than the excited state absorption, while reverse saturable absorption appears in HfS2 due to the two-photon absorption. The figure of merit values of ZrS2 (≈4.30 ± 0.12 × 10−15 esu cm) and HfS2 (≈6.0 ± 1.4 × 10−15 esu cm) are much larger than those of MoS2 and graphene in ultrafast nonlinear optical performance at the wavelength of 800 nm.  相似文献   

2.
In order to study the electronic structure of TiS2, ZrS2 and HfS2, selfconsistent charge Xα discrete variational calculations of clusters MeS68- (Me = Ti, Zr, Hf) have been performed. The results obtained are consistent with band structure calculations. The covalency of the chemical bonding is shown to increase in the series TiS2-ZrS2-HfS2, which corresponds to the atomization energy in the series. The results are applied in the interpretation of X-ray emission, photoelectron and optical spectra.  相似文献   

3.
The nuclear quadrupole interaction at181Ta on Hf/Zr-sites in ZrS2, HfS2, HfSe2, and HfTe5 exhibits anomalies as a function of temperature, indicative of lattice instabilities. We interpret our observations as being due to static or low frequency structural distortions perpendicular to the layers and take these as evidence for Ruelle's turbulent crystal.  相似文献   

4.
The tranmission spectra and the wavelength-modulated transmission spectra of ZrS2 and HfS2 were measured simultaneously over the temperature range from 1.9 to 300K, and structures in the spectra due to the indirect allowed transitions including excitonic effects were clearly observed. Comparing with the band structure calculations, these correspond to Γ2 å L +1 and Γ2 å M+1 transitions.  相似文献   

5.
We report on solution processable organic field effect transistors prepared using a poly(3‐hexylthiophene)–ZnO nanoparticles composite as channel semiconductor material and cross‐linked polyvinyl alcohol as gate insulator. Our transistors show a field effect mobility of 0.35 ± 0.06 cm2/V s, threshold voltage of –1.30 ± 0.11 V, and Ion/Ioff ratio of (1.0 ± 0.1) × 103. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

6.
Absolute cross sections for electron-impact single ionization, dissociative excitation and dissociative ionization of the ethynyl radical ion (C2D+)^+) have been measured for electron energies ranging from the corresponding reaction thresholds to 2.5 keV. The animated crossed electron-ion beam experiment is used and results have been obtained for the production of C2D2+, C2+, C2+_2^+ , CD+, C+ and D+. The maximum of the cross section for single ionization is found to be (2.01 ± 0.02) × 10-17 cm2, at the incident electron energy of 105 eV. Absolute total cross sections for the various singly charged fragments production are observed to decrease by a factor of almost three, from the largest cross-section measured for C+, over C2+_2^+ and CD+ down to that of D+. The maxima of the cross sections are obtained to be (14.5 ± 0.5) × 10-17 cm2 for C2+_2^+, (12.1 ± 0.1) × 10-17 cm2 for CD+, (27.7 ± 0.2) × 10-17 cm2 for C+ and (11.1 ± 0.8) × 10-17 cm2 for D+. The smallest cross section is measured to be (1.50 ± 0.04) × 10-18 cm2 for the production of the doubly charged ion C2+. Individual contributions for dissociative excitation and dissociative ionization are determined for each singly-charged product. The cross sections are presented in closed analytic forms convenient for implementation in plasma simulation codes. Kinetic energy release distributions of dissociation fragments are seen to extend from 0 to 6 eV for the heaviest fragment C2+_2^+, up to 11.0 eV for CD+, 14.2 eV for C+ and 11.2 eV for D+ products.  相似文献   

7.
The CF(X2Π) radical has been re-investigated with vacuum ultraviolet photoelectron spectroscopy. Two bands were observed and assigned to the ionisations CF+(X1Σ+)←CF(X2Π) and CF+(a3Π)← CF(X2Π). The first band, which has been observed previously, has an adiabatic ionisation energy of (9.11±0.02) eV and a vertical ionisation energy of (9.55±0.02) eV. For the second band, three vibrational components were observed with the first, the most intense, at an ionisation energy of (13.94±0.02) eV. Analysis of the vibrational structure in the two observed bands allowed ωe and re to be determined as 1810±30 cm−1 and 1.154±0.005 Å, respectively for the first ionic state, CF+(X1Σ+), and 1614±30 cm−1 and 1.213±0.005 Å, respectively for the second ionic state, CF+(a3Π). Comparison of the ionisation energies and spectroscopic constants obtained has been made with values obtained from recent multi-reference configuration interaction calculations.  相似文献   

8.
Auger electron spectra have been recorded when oxygen is adsorbed on a Ni(111) single crystal surface. For the coverage range θ < 1, an analysis of the plot of the peak to peak height (H) of the oxygen KVV (516 eV) transition versus the total number of molecules cm2? impinging on the surface (molecular beam dosing) shows agreement with the kinetic mechanism proposed by Morgan and King [Surface Sci. 23 (1970) 259] for the adsorption of oxygen on polycrystalline nickel films. In this coverage range, no energy shifts of the nickel or oxygen Auger peaks were recorded.At coverages θ > 1 (standard dosing procedure) shifts in the valence spectra M2, 3VV (61 eV) and L3M2, 3V (782 eV) of ?2.3 eV and ?1.8eV respectively are recorded at 1.4 × 10?2 torr-sec. Up to these coverages no shift of the L3VV transition (849 eV) is observed. A chemical shift of ?2.1 eV is recorded in the L3M2, 3M2, 3 Auger transition (716 eV) at 1.4 × 10?2 torr-sec.In the coverage range θ > 1, shifts in the energy of the oxygen Auger peaks are observed. At 5.8 × 10?3 torr-sec. the KVV (516 eV) and KL1V (495.2 ± 0.3 eV) transitions show shifts of ?1.5 eV and ?(1.0 ±0.3) eV respectively. No shift up to this coverage is recorded in the KL1L1 (480.6 ± 0.3 eV) transition.  相似文献   

9.
We have used the technique of chemical vapour transport to prepare needle shaped single crystal of ZrS3. Results of the measurements of d.c. resistivity. Hall coefficient and thermoelectric power of the temperature range 100–500 K are reported. All the samples exhibited semiconducting behaviour with a room temperature resistivity of about 15 Ω-cm and an activation energy of 0.20±0.02 eV. Room temperature thermoelectric power is -850 μVK?1 and the dominant carriers are electrons. The thermoelectric power varies as (1/T), a behaviour associated with a typical semiconductor. Mobility at low temperatures is limited by ionized impurity scattering and is given by μ1 = 6.5 × 10?2T3/2 cm2V7-1 sec?1. At high temperatures, phonon scattering is dominant and the mobility is given by μ2 = 1.35 × 10+5T?32 cm2V?1 sec?1.  相似文献   

10.
Stabilities of hydrogen atoms at the interstitial (H0i), cation and anion sites (H0sc and H0sa) in KCl have been studied with ESR and thermoluminescence. The close pair between H0i and S? formed by UV-irradiation of KCl:SH? recombines first with the activation energy of 0.17±0.02 eV following the emission of light and then H0i becomes mobile with the energy of 0.20±0.02 eV. The energies determined from the decay of ESR signal intensity of H0sc and H0sa are 0.24±0.02 eV and 0.43±0.03 eV, respectively.  相似文献   

11.
A.C. electrical conductivity of pottasium perchlorate (KP) has been measured in the temperature range 25–325°C at frequencies ranging from 50–500 Hz using an automated technique. Three regions with activation energies. 1.08 ± 0.02, 0.66 ± 0.01 and 0.39 ± 0.04eV are observed in ln(σT) vs 1/T plots at frequencies < - 50 Hz. Dielectric loss measurements on KP samples doped with CrO42? and SO42? ions show the presence of impurity-vacancy complexes with reorientation energies of 0.99 ±0.02 and 1.07 ± 0.01 eV respectively. The results are interpreted in terms of a defect model which highlights the role of various conduction and relaxation mechanisms in the a.c. electrical properties of the material.  相似文献   

12.
Conversion electron measurements with an electrostatic spectrometer proved the existence of the 1,565±6 eV transition in201Hg. The conversion intensity ratios,N 1/N 2 =1.2±0.2,N 1/N 3=1.1±0.2,N 2/N 3=0.92±0.15,N 4/N 3=0.03± 0.02 andN 5/N 3=0.04 ±0.02 were determined. These values agree with our calculations for the M1±E2 multipolarity with theE2/M1 mixing ratioδ 2=(l.l±0.3)xl0?4 and exclude all pure multipolarities withL≦4. The total conversion coefficient for the aboveM1 +E2 mixture was evaluated to be (4.7±0.7)× 104. The reducedB(M1, 1/2→3/2) probability was derived to be (3.9 ±1.2) × 10?3 (e?/2Mc)2. The natural widths of theN-subshell conversion lines in mercury were found to beΓ(N 1)=8.3± 1.5,Γ(N 2) =5.8±1.5 and Γ(N 3) =6.5±1.0 eV. Monte Carlo calculations of electron scattering in matter yielded the conversion line shapes in qualitative agreement with the experiment.  相似文献   

13.
The photoexcitation of isomer 157m Gd (11/2-, 426 keV, T 1/2 = 18.5 μs) in reaction (γ, γ′) was studied on the pulsed nonferromagnetic betatron at St. Peterburg State University. Only two strong intermediate structures (IntS) with E 1 = 4.0 ± 0.1 MeV, (σΓ)1iso = 5 eV b and E 2 = 5.3 ± 0.1 MeV, (σΓ)2iso = 40 eV b, respectively, were found. Comparison of the spectra IntS of isomers 157m Gd and 181m Ta demonstrates the weak correlation between isomer excitation probabilities and ground states deformation parameters.  相似文献   

14.
Nanostructured α‐Fe2O3 thin film electrodes were deposited by aerosol‐assisted chemical vapour deposition (AACVD) for photoelectrochemical (PEC) water splitting on conducting glass substrates using 0.1 M methanolic solution of Fe(acac)3. The XRD analysis confirmed that the films are highly crystalline α‐Fe2O3 and free from other iron oxide phases. The highly reproducible electrodes have an optical bandgap of ~2.15 eV and exhibit anodic photocurrent. The current–voltage characterization of the electrodes reveals that the photocurrent density strongly depended on the film morphology and deposition temperature. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology with the change in deposition temperature. The films deposited at 450 °C have nanoporous structures which provide a maximum electrode/electrolyte interface. The maximum photocurrent density of 455 µA/cm2 was achieved at 0.25 V vs. Ag/AgCl/3M KCl (~1.23 V vs. RHE) and the incident photon to electron conversion efficiency (IPCE) was 23.6% at 350 nm for the electrode deposited at 450 °C. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)  相似文献   

15.
In order to elucidate the nature of Lewis bases in layered transition metal dichalcogenides (TX2), ammoniated titanium disulfide, (NH3)yTiS2 with 0.4 ? y ? 0.6, has been synthesized using stoichiometric TiS2 and investigated by X-ray diffraction, vapor pressure measurements, thermogravimetric analysis, differential scanning calorimetry, and SQUID magnetrometry. These intercalation compounds lose ammonia rapidly at ambient temperature to form primarily a stage II structure. Upon heating, about half of the ammonia is weakly bound (deintercalation enthalpy ?2.6 kcal/mol) and leaves the TiS2 host at low temperatures (?75°C), whereas the other half is bound more strongly (deintercalation enthalpy ?6.3 kcal/mol) and deintercalates only at higher temperatures (?150°C). The more strongly bound ammonia is identified as NH4+, and an electron is donated to the TiS2 conduction band for each NH4+-ion present. Hence, the ionic formulation (NH4+)y' (NH3)y'TiS2y' - best describes these materials, where the NH4+ ions are analogous to alkali-metal cations M+ in metal-ammonia intercalation complexes. The presence of a substantial concentration of NH4+ provides a simple explanation of the unusual observation that the C3 axis of NH3 is parallel to the TiS2 layers. The results of this study show that redox reactions do indeed play an important role in ammonia intercalation into TiS2 and probably also into other TX2 hosts.  相似文献   

16.
The specific heats of the semiconducting compounds ZrSe3 and ZrS3 have been measured in the temperature range between 8 and 200 K. At the lowest values of T, the ZrSe3 measurements can be analyzed in terms of the familiar Debye T3 law yielding a characteristic Debye temperature at absolute zero θD(0) = 110 ± 2 K in satisfactory agreement with the value extracted from the available experimental sound velocities. In contrast, the low-temperature ZrS3 measurements do not behave according to the Debye law. This is interpreted as resulting from a strong mixing of low-lying optical modes with the acoustical branches, and reflects a more pronounced one-dimensional character of ZrS3 compared to ZrSe3.  相似文献   

17.
Luminescence spectra of single crystals of CsI:In+ excited in the A(304 nm), B(288 nm), C(268 nm) and D(257 nm) absorption bands have been studied in the temperature range 4.2–300 K. Excitation in the A band at 4.2 K gives rise to the principal emission at 2.22 eV accompanied by a partly-overlapping weak band at 2.49 eV. An additional emission band at about 2.96 eV is observed on excitation in the B, C or D bands. Yet another emission band located at 2.67 eV is excited only in the D band. The relative intensities of the bands are very sensitive to excitation wavelength as well as to temperature. The origin of all these bands is assigned in terms of a model for the relaxed excited states (RES). All the luminescence spectra were resolved into an appropriate number of skew-Gaussian components. Moments analysis leads to a value of (1.35 ± 0.02) × 1013 rad s-1 for the effective frequency (ωeff) of lattice vibrations coupled to the RES. At the lowest temperature, the radiative decay times of each of the intracenter emission bands (2.22, 2.49 and 2.96 eV) show a slow decay ( ~ 10–100 μs) and a fast decay ( ~ 10–100 ns). The 2.96 eV band, which is assigned to an emission process which is the inverse of the D-band absorption, exhibits a single decay mode ( ~ 10 μs). The intrinsic radiative decay rates (k1, k2), the one-phonon transition rate (K) and the second-order spin-orbit splitting (D) for the RES responsible for the principal emission are: k1 = (6.0±-0.3)×103 s-1, k2 = (1.33±-0.06)×105 s-1, K = (2.4±-0.4)×107 s-1 and D = (13.8±-0.5) cm-1.  相似文献   

18.
Gallium antimonide (GaSb) films were deposited onto fused silica and n-Si (100) substrates by coevaporating Ga and Sb from appropriate evaporation sources. The films were polycrystalline in nature. The size and the shape of the grains varied with the change in the substrate temperature during deposition. The average surface roughness of the films was estimated to be 10 nm. Grain boundary trap states varied between 2×1012 and 2.2×1012 cm?2 while barrier height at the grain boundaries varied between 0.09 eV and 0.10 eV for films deposited at higher temperatures. Stress in the films decreased for films deposited at higher temperatures. XPS studies indicated two strong peaks located at ~543 eV and ~1121 eV for Sb 3d3/2 and Ga 2p3/2 core-level spectra, respectively. The PL spectra measured at 300 K was dominated by a strong peak located ~0.55 eV followed by two low intensity peaks ~0.63 eV and 0.67 eV. A typical n-Si/GaSb photovoltaic cell fabricated here indicated V oc~311 mV and J~29.45 mA/cm2, the density of donors (N d)~3.87×1015 cm?3, built in potential (V bi)~0.48 V and carrier life time (τ)~28.5 ms. Impedance spectroscopy measurements indicated a dielectric relaxation time ~100 μs.  相似文献   

19.
A highly efficient planar heterojunction OSC based on zinc phthalocyanine (ZnPc)/fullerene (C60) by controlling the orientation of the ZnPc by using copper iodide (CuI) as the interfacial layer is reported. The proportion of face-on ZnPc molecules was increased significantly on the CuI layer compared to the layer without the CuI layer, which was analyzed with wide-angle X-ray scattering (WAXS) and optical absorption. The power conversion efficiency (PCE) of the orientation controlled planar heterojunction OSC was remarkably enhanced to 3.2 ± 0.1% compared with 1.2 ± 0.1% of the conventional OSCs without the control of the molecular orientation. By inserting the 3-nm-thick CuI layer, JSC, VOC and FF have increased from 4.6 ± 0.2 to 8.9 ± 0.2 mA cm?2, from 0.48 ± 0.01 to 0.59 ± 0.02 V, and from 0.56 ± 0.01 to 0.61 ± 0.02, respectively. VOC enhancement is discussed with the result of the ultraviolet photoemission spectra (UPS) measurements.  相似文献   

20.
Valence band offsets ΔEVBM at ZnSx O1–x/Cu(In,Ga)(Se,S)2 (CIGSSe) heterojunctions have been studied by photoemission spectroscopy (XPS, UPS) as a function of composition x in sputtered ZnSx O1–x films. In the composition range from ZnO to ZnS we found ΔEVBM between –(2.1 ± 0.3) eV and –(0.8 ± 0.4) eV, respectively. Considering the optical band gaps, the conduction band offsets ΔECBM range from –(0.1 ± 0.3) eV to +(1.4 ± 0.4) eV. These results suggest that sputtered ZnSx O1–x is suitable as substitution for the CdS buffer and ZnO window layers in standard chalcopyrite‐based solar cells. Current–voltage characteristics of the solar cells have been investigated as a function of the composition x. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

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