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1.
In this paper, we present the effects of ultrathin Si interfacial layer on the physical and electrical properties of GaAs MOS capacitors fabricated using RF-sputtered HfAlOx gate dielectric. It is found that HfAlOx/Si/n-GaAs stack exhibits excellent electrical properties with low frequency dispersion (∼4.8%), hysteresis voltage (0.27 V) and interface trap density (1.3 × 1012 eV−1 cm−2). The current density of 3.7 × 10−5 A/cm2 is achieved with an equivalent-oxide-thickness of 1.8 nm at VFB + 1 V for Si-passivated HfAlOx films on n-GaAs. X-ray photoelectron spectroscopy (XPS) analysis shows that the suppression of low-k interfacial layer formation is accomplished with the introduction of ultrathin Si interface control layer (ICL). Thus the introduction of thin layer of Si between HfAlOx dielectrics and GaAs substrate is an effective way to improve the interface quality such as low frequency dispersion, hysteresis voltage and leakage current. Additionally, current conduction mechanism has been studied and the dominant conduction mechanisms are found to be Schottky emission at low to medium electric fields and Poole-Frenkel at high fields and high temperatures under substrate injection. In case of gate injection, the main current conduction at low field is found to be the Schottky emission at high temperatures.  相似文献   

2.
The nanostructure n-ZnO/p-Si heterojunction diode was fabricated by sol–gel method. The structural and morphological properties of the nanostructure ZnO film have been investigated. The X-ray diffraction spectra indicated that the films are of polycrystalline nature. The scanning electron microscopy images indicate that the surface morphology of ZnO film is almost homogeneous and the ZnO film is consisted of the circular formed with coming together of the nanoparticles. The electrical characterization of nanostructure n-ZnO/p-Si heterojunction diode has been investigated by current–voltage characteristics. The ideality factor (n) of the diode was found for different ambient temperatures and the obtained 6.40 value for 296 K is higher than unity due to the interface states between the two semiconductor materials and series resistance. The values of n increased with decreasing ambient temperature. The reverse current of the diode increased with illumination intensity of 100 mW cm−2 and the diode gave a maximum open circuit voltage Voc of 0.19 V and short-circuits current Isc of 8.03 × 10−8 A.  相似文献   

3.
This paper reports the growth and spectroscopic characterization of Er3+:Sr3Y(BO3)3 crystal. Er3+:Sr3Y(BO3)3 crystal with dimensions up to ∅20×35 mm3 has been grown by Czochralski method. The polarized spectroscopic properties of Er3+:Sr3Y(BO3)3 crystal were investigated. Based on the Judd-Ofelt theory, the effective intensity parameters Ωt were obtained: Ω2=1.71×10−20 cm2, Ω4=1.39×10−20 cm2, Ω6=0.74×10−20 cm2 for π-polarization, and Ω2=1.77×10−20 cm2, Ω4=1.44×10−20 cm2, Ω6=0.65×10−20 cm2 for σ-polarization. The emission cross-section σem was calculated to be 4.75×10−21 cm2 for π-polarization at 1536 nm and 6.30×10−21 cm2 for σ-polarization at 1537 nm. The investigated results showed that Er3+:Sr3Y(BO3)3 crystal may be regarded as a potential laser host material for 1.55 μm IR solid-state lasers.  相似文献   

4.
Physical and electrical properties of sputtered deposited Y2O3 films on NH4OH treated n-GaAs substrate are investigated. The as-deposited films and interfacial layer formation have been analyzed by using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). It is found that directly deposited Y2O3 on n-GaAs exhibits excellent electrical properties with low frequency dispersion (<5%), hysteresis voltage (0.24 V), and interface trap density (3 × 1012 eV−1 cm−2). The results show that the deposition of Y2O3 on n-GaAs can be an effective way to improve the interface quality by the suppression on native oxides formation, especially arsenic oxide which causes Fermi level pinning at high-k/GaAs interface. The Al/Y2O3/n-GaAs stack with an equivalent oxide thickness (EOT) of 2.1 nm shows a leakage current density of 3.6 × 10−6 A cm−2 at a VFB of 1 V. While the low-field leakage current conduction mechanism has been found to be dominated by the Schottky emission, Poole-Frenkel emission takes over at high electric fields. The energy band alignment of Y2O3 films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y2O3/n-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively.  相似文献   

5.
We demonstrated the tunable contact resistance in pentacene thin film transistor (TFT) by inserting an organic-inorganic hybrid interlayer between Au electrode and pentacene layer. The contact resistance of pentacene-TFT varies with concentration of pentacene-TFT varies with concentration of MoOx in organic-inorganic hybrid interlayer. MoOx in organic-inorganic hybrid interlayer. The contact resistance of the device with 55 wt% MoOx doped pentacene interlayer is about 7.8 times smaller than that of device without interlayer at the gate voltage of −20 V. Comparing the properties of pentacene-TFT without interlayer, the performance of the pentacene-TFT with 55 wt% MoOx doped pentacene was significantly improved: saturation mobility increased from 0.39 to 0.87 cm2/V s, threshold voltage reduced from −21.3 to −7.2 V, and threshold swing varied from 3.75 to 1.39 V/dec. Our results indicated that the organic-inorganic hybrid interlayer is an effective way to improve the performance of p-channel OTFTs.  相似文献   

6.
In view of CdS growth is very impotent for technological importance especially solar applications; synthesis of this material remains a topic of great interest for researchers by means of an economically and technically viable method. In the present paper, Cd/CdS/n–Si/Au–Sb sandwich structure has been grown by Successive Ionic Layer Adsorption and Reaction (SILAR) technique. For investigating the structural properties, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) measurements have been performed and it has been seen that films exhibit polycrystalline behavior. The capacitance–voltage (CV) and conductance/w-voltage (G/wV) characteristics of Cd/CdS/n–Si/Au–Sb structure have been investigated by considering series resistance and interface states effects. These measurements have been done in the −4 V, 4 V voltage range and in the frequency range of 10 kHz–3 MHz at room temperature. It is seen that, the series resistance (Rs) and interface state density have been strongly depend on frequency. The barrier height, donor concentration, diffusion potential parameters have been determined from the linear C−2V plot. The barrier height values are obtained between 0.495 and 0.796 eV and doping density values have been ranged from 1.455 × 1014 to 1.999 × 1014 cm−3respectively. The capacitance–frequency (Cf) and conductance/w-frequency (G/wf) characteristics of Cd/CdS/n–Si/Au–Sb structures have been measured at the various biases 0.00–0.14 V at room temperature. The energy distribution of the interface states (Nss) and their relaxation time (τ) have been determined from the forward bias capacitance–frequency characteristics. The Nss and τ values have ranged from 2.01 × 1012 cm−2 eV−1and 9.68 × 10−4 s in (Ec-0.45) eV–2.86 × 1013 cm−2 eV−1 and 3.81 × 10−4 s in (Ec-0.75) eV, respectively.  相似文献   

7.
The photocarrier mobility of Fe 0.03 wt%-doped potassium lithium tantalate niobate (K0.95Li0.05Ta0.61Nb0.39O3) was investigated by time-of-flight (TOF) measurement. The longitudinal photocarrier response due to pulsed excitation leads to values of the drift mobility of μh = 1.45 × 10−2 cm2/V s for holes, μe = 0.325 × 10−2 cm2/V s for electrons, and a value for the range of holes (μτ)h = 4.38 × 10−5 cm2/V at room temperature and at low field 3 KV/cm. The response time of holes and electrons (or the relaxation time) is determined to be 3.02 × 10−3 s and 3.74 × 10−3 s, respectively. The mobility of holes strongly depends on the field strength, and is observed to decrease with increasing bias field.  相似文献   

8.
A more noble and biocompatible Ti alloy was achieved at fluence of 140 J cm−2 where the implant indicated a higher degree of hardness (825HV), higher corrosion resistance (−0.21 V) and highest hydrophilicity (i.e. θc = 37°) compared with 70° of the control sample. These values corresponded to 58 and 39 mN m−1 of surface tension respectively. The laser treated samples at 140 J cm−2 showed higher wettability characteristics than mechanically roughened surface. Cell growth and their spreading condition in a specific area were analyzed by SEM and Image J Program software. Clearly, more cells were attached (1.2 × 105) to and spread (488 μm2) over the surface at 140 J cm−2 than in any other condition. Pathologically, the treated samples indicated no sign of infection.  相似文献   

9.
Over 8000 line positions and intensities of phosphine (PH3) at 3 μm have been measured at 0.0115 cm−1 resolution with the McMath-Pierce Fourier Transform spectrometer at Kitt Peak. The observed line intensities ranged from 4.13 × 10−6 to 4.69 × 10−2 cm−2 atm−1 at 296 K, for line positions between 2724.477 and 3601.652 cm−1. This region spans eight interacting vibrational states: 3ν2 (2940.8 cm−1), 2ν2 + ν4 (3085.6 cm−1), ν2 + 2ν4 (3214.9 cm−1), ν1 + ν2 (3307.6 cm−1), ν2 + ν3 (3310.5 cm−1), 3ν4 (∼3345 cm−1), ν1 + ν4 (3426.9 cm−1), and ν3 + ν4 (3432.9 cm−1). Assignments have been determined for all the bands except 3ν4 (a weak band in a highly congested area) for a total of 4232 transitions. The total integrated intensity for this region is 5.70 cm−2 atm−1 near 296 K, and assigned lines account for 79% of the observed absorption. The two strongest bands in the region are ν1 + ν4 and ν3 + ν4 with band strengths at 296 K of 1.61 and 2.01 cm−2 atm−1, respectively. An empirical database of PH3 line parameters (positions, intensities, and assignments) is now available. Lower state energies (corresponding to assignments from this study) and line widths from the literature are included; default values are used for unassigned features.  相似文献   

10.
Five-layered Si/SixGe1−x films on Si(1 0 0) substrate with single-layer thickness of 30 nm, 10 nm and 5 nm, respectively were prepared by RF helicon magnetron sputtering with dual targets of Si and Ge to investigate the feasibility of an industrial fabrication method on multi-stacked superlattice structure for thin-film thermoelectric applications. The fine periodic structure is confirmed in the samples except for the case of 5 nm in single-layer thickness. Fine crystalline SixGe1−x layer is obtained from 700 °C in substrate temperature, while higher than 700 °C is required for Si good layer. The composition ratio (x) in SixGe1−x is varied depending on the applied power to Si and Ge targets. Typical power ratio to obtain x = 0.83 was 7:3, Hall coefficient, p-type carrier concentration, sheet carrier concentration and mobility measured for the sample composed of five layers of Si (10 nm)/Si0.82Ge0.18 (10 nm) are 2.55 × 106 /°C, 2.56 × 1012 cm−3, 1.28 × 107 cm−2, and 15.8 cm−2/(V s), respectively.  相似文献   

11.
High quality Tm-doped YAlO3 (Tm:YAlO3) single crystals were obtained along crystallographic b-axis by the Czochralski technique. Optical absorption and fluorescence spectra for Tm3+ in YAlO3 crystals were investigated at room temperature. Based on Judd-Ofelt approach, the intensity parameters Ωt (t = 2, 4, 6) of Tm:YAlO3 were calculated to be Ω2 = 0.93 × 10−20  cm2, Ω4 = 2.23 × 10−20 cm2, and Ω6 = 1.12 × 10−20 cm2. The spectral parameters such as experimental and theoretical oscillator strengths, radiative transition probabilities, radiative lifetime and the fluorescence branching ratio were also obtained. All results indicate that Tm:YAlO3 is a potential candidate for compact, efficient mid-infrared lasers with laser diode pumping.  相似文献   

12.
Efficient white organic light-emitting diodes (WOLEDs) are fabricated with a thin layer of 9,10-bis (2-naphthyl) anthracene (ADN) doped with Rubrene as the source of white emission. A device with the structure of ITO/NPB (70 nm)/ADN: 0.5% Rubrene (30 nm)/Alq3 (50 nm)/MgAg shows a maximum current efficiency of 3.7 cd/A, with the CIE coordinates of x=0.33, y=0.43. The EL spectrum of the devices and the CIE coordinates remains almost the same when the voltage is increased from 10 to 15 V and the current efficiency remains quite stable with the current density increased from 20 to 250 mA/cm2.  相似文献   

13.
ZnO:Eu3+, Li+ films prepared by the dip-coating method were characterized by photoluminescence (PL) and electroluminescence (EL). When the ZnO:Eu3+, Li+ films were excited using UV light with energy corresponding to the band-to-band excitation of the host matrix, the PL spectra showed emissions from both ZnO and Eu3+ ions, while their EL spectra showed emissions only from Eu3+ ions, and no emission from ZnO could be detected. It is found that the EL emission intensity B is dependent on the applied voltage, B=Bo exp(−bV−1/2). With increasing frequency, the EL intensity dramatically increases at lower frequencies (<1000 Hz), and then increases gradually at higher frequencies (>1000 Hz).  相似文献   

14.
We report a study of InSb nanoobjects (quantum dots and quantum rings) grown on InAs-rich surface by liquid phase epitaxy. Characterization of the sample surface was performed using atomic force microscopy (AFM). The bimodal formation of the uncapped InSb quantum dots (QDs) was observed for the growing on a binary InAs substrate. Uniform high-density (1 × 1010 cm−2) quantum dots with a height of 3 nm were obtained at T = 420-430 °C, whereas low-density (5 × 108 cm−2) big quantum dots were 9 nm in height. As a buffer layer, lattice-matched InAsSb0.12P0.25 solid solution was deposed on InAs substrate using metal-organic vapour phase epitaxy. Deposition from the InSb melt on the buffer layer resulted in the formation of InSb nanoobjects with density as high as 3 × 1010 cm−2.  相似文献   

15.
The absorption spectrum of ozone, 16O3, has been recorded by CW-cavity ring down spectroscopy in the 6625-6830 cm−1 region. The typical sensitivity of these recordings (αmin ∼ 3 × 10−10 cm−1) allows observing very weak transitions with intensity down to 2 × 10−28 cm/molecule. 483 and 299 transitions have been assigned to the 2ν1 + 3ν2 + 3ν3A-type band and to the 2ν1 + 4ν2 + 2ν3B-type band, respectively, which are the highest frequency bands of ozone recorded so far under high resolution. Rovibrational transitions with J and Ka values up to 46 and 12, respectively, could be assigned. Despite well-known difficulties to correctly reproduce the energy levels not far from the dissociation limit, it was possible to determine the parameters of an effective Hamiltonian which includes six vibrational states, four of them being dark states. The line positions analysis led to an rms deviation of 8.5 × 10−3 cm−1 while the experimental line intensities could be satisfactorily reproduced. Additional experiments in the 5970-6021 cm−1 region allows detecting the (233) ← (010) hot band reaching the same upper state as the preceding cold band. From the effective parameters of the (233) state just determined and those of the (010) level available in the literature, 329 transitions could be assigned and used for a further refinement of the rovibrational parameters of the effective Hamiltonian leading to a value of 7.6 × 10−3 cm−1 for the global rms deviation. The complete list of the experimentally determined rovibrational energy levels of the (233), (242), and (520) states is given. The determined effective Hamiltonian and transition moment operators allowed calculating a line list (intensity cut off of 10−28 cm/molecule at 296 K), available as Supplementary material for the 6590-6860 and 5916-6021 cm−1 regions. The integrated band strength values are 1.75 × 10−24 and 4.78 × 10−25 cm/molecule at 296 K for the 2ν1 + 3ν2 + 3ν3A-type band and to the 2ν1 + 4ν2 + 2ν3B-type band, respectively, while the band intensity value of the (233) ← (010) is estimated to be 1.03 × 10−24 cm/molecule.  相似文献   

16.
Er:YSGG single crystals with good optical quality were grown by Czochralski method. X-ray diffraction (XRD) measurements show that the crystal lattice parameters of the 30 at.% Er3+-doped YSGG crystal were a=b=c=12.4640±0.0065 Å, α=β=γ=90°. The doping concentration of Er3+ in YSGG was calculated. The absorption spectrum and photoluminescence spectra of Er:YSGG crystal were studied at room temperature. Based on Judd-Ofelt (J-O) theory, the J-O intensity parameters Ωt (t=2, 4, 6), the experimental and theoretical oscillator strengths were calculated using the absorption spectrum. The intensity parameters Ωt (t=2,4,6) obtained to be Ω2=0.23×10−20 cm2, Ω4=0.86×10−20 cm2, Ω6=0.37×10−20 cm2, respectively. With these intensity parameters, the line strengths, oscillator strengths, transition probabilities, fluorescence branching ratios and radiation lifetimes were calculated. The photoluminescence spectra and excitation spectrum of Er:YSGG were measured and studied.  相似文献   

17.
The current-voltage (I-V) characteristics of Al/p-Si Schottky barrier diodes (SBDs) with native insulator layer were measured in the temperature range of 150-375 K. The estimated zero-bias barrier height ΦB0 and the ideality factor n assuming thermionic emission (TE) theory show strong temperature dependence. Evaluation of the forward I-V data reveals an increase of zero-bias barrier height ΦB0 but decrease of ideality factor n with increase in temperature. The conventional Richardson plot exhibits non-linearity below 250 K with the linear portion corresponding to activation energy of 0.41 eV and Richardson constant (A*) value of 1.3 × 10−4 A cm−2 K−2 is determined from intercept at the ordinate of this experimental plot, which is much lower than the known value of 32 A cm2 K2 for holes in p-type Si. Such behavior is attributed to Schottky barrier inhomogene ties by assuming a Gaussian distribution of barrier heights (BHs) due to barrier height inhomogeneities that prevail at interface. Also, ΦB0 versus q/2kT plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of ΦB0 = 1.055 eV and σ0 = 0.13 V for the mean BH and zero-bias standard deviation have been obtained from this plot, respectively. Thus, the modified versus q/kT plot gives ΦB0 and A* as 1.050 eV and 40.08 A cm−2 K−2, respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 40.03 A cm−2 K−2 is very close to the theoretical value of 32 A K−2 cm−2 for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/p-Si Schottky barrier diodes with native insulator layer can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights.  相似文献   

18.
Y2O3 transparent ceramics with different Nd concentration (0.1-7.0at%) were fabricated using ZrO2 as additive. All the samples exhibit high transparency over a broad spectral region. The elements (Y, O and Nd) are uniformly distributed in the ceramic body, and the average grain size increases with Nd content. Based on the absorption spectrum, the Judd-Ofelt intensity parameters are calculated (Ω2=4.364×10−20 cm2, Ω4=3.609×10−20 cm2 and Ω6=2.919×10−20 cm2). The absorption coefficients increase linearly with Nd3+ doping concentration. The absorption cross-section at 804 nm and stimulated emission cross-section at 1078 nm are calculated to be 1.54×10−20 and 7.24×10−20 cm2, respectively. All the emission bands exhibit the highest emission intensities with 1.0at% Nd3+ ion content, while the lifetime decreases dramatically from 321.5 μs (0.1at% Nd) to 17.9 μs (7.0at% Nd). According to the emission spectra and measured lifetime, the optimum doping concentration of Nd3+ ion in Y2O3 transparent ceramic might be around 1.0at%.  相似文献   

19.
Au/GaN/n-GaAs structure has been fabricated by the electrochemically anodic nitridation method for providing an evidence of achievement of stable electronic passivation of n-doped GaAs surface. The change of the electronic properties of the GaAs surface induced by the nitridation process has been studied by means of current-voltage (I-V) characterizations on Schottky barrier diodes (SBDs) shaped on gallium nitride/gallium arsenide structure. Au/GaN/n-GaAs Schottky diode that showed rectifying behavior with an ideality factor value of 2.06 and barrier height value of 0.73 eV obeys a metal-interfacial layer-semiconductor (MIS) configuration rather than an ideal Schottky diode due to the existence of GaN at the Au/GaAs interfacial layer. The formation of the GaN interfacial layer for the stable passivation of gallium arsenide surface is investigated through calculation of the interface state density Nss with and without taking into account the series resistance Rs. While the interface state density calculated without taking into account Rs has increased exponentially with bias from 2.2×1012 cm−2 eV−1 in (Ec−0.48) eV to 3.85×1012 cm−2 eV−1 in (Ec−0.32) eV of n-GaAs, the Nss obtained taking into account the series resistance has remained constant with a value of 2.2×1012 cm−2 eV−1 in the same interval. This has been attributed to the passivation of the n-doped GaAs surface with the formation of the GaN interfacial layer.  相似文献   

20.
Magnetoresistance and Hall coefficient of air-stable potassium-intercalated graphite sheets (hereafter abbreviated as K-PGS) were determined at room temperature. The magnitude of the magnetoresistance and the absolute value of Hall coefficient of K-PGS decreased with increasing potassium content of K-PGS, nK/nC. Two-carrier model was used for calculating carrier density and mobility. The electron density increased with increasing nK/nC: 3.07×1020 cm−3 (nK/nC=0.005), 5.67×1020 cm−3 (nK/nC=0.008) and 6.40×1020 cm−3 (nK/nC=0.011). The value of the electron density of K-PGS with nK/nC=0.011 (nominal composition KC91) was about 80% of the reported value, 7.8×1020 cm−3, for KC48 (nK/nC=0.021) prepared from HOPG (highly oriented pyrolytic graphite). The mobility decreased with increasing nK/nC: 2.11×103 cm2 V−1 s−1 (nK/nC=0.005), 1.42×103 cm2 V−1 s−1 (nK/nC=0.008) and 1.34×103 cm2 V−1 s−1 (nK/nC=0.011). The value of the mobility of K-PGS with nK/nC=0.011 was about 60% of the reported value (2300 cm2 V−1 s−1) for KC48 prepared from HOPG.  相似文献   

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