Electrical and photovoltaic characteristics of sodium copper chlorophyllin/n-type silicon heterojunctions

Heterojunctions of p-type sodium copper chlorophyllin (p-SCC)/n-type silicon (n-Si) were prepared by deposition of p-SCC film on n-Si wafers using spray-pyrolysis technique. Current-voltage and capacitance-voltage measurements of Au/p-SCC/n-Si/In heterojunctions were performed to discuss the electrical properties of these heterostructures. Rectifying characteristics were observed, which are definitely of the diode type. The current-voltage measurements suggest that the forward current in these junctions involves tunnelling and the results showed that the forward current can be explained by a multi-tunnelling capture-emission model in which the electron emission process dominates the carrier transport mechanism. On the other hand, the reverse current is probably limited by the same conduction process. The capacitance-voltage behavior indicates an abrupt heterojunction model is valid for Au/p-SCC/n-Si/In heterojunctions and the junction parameters such as, built-in potential, V_D, carrier concentration, N, the width of depletion layer, W, were obtained. The temperature and frequency dependence of the measured capacitance were also studied. The loaded I-V characteristics under white illumination provided by tungsten lamp (80 mW/cm²) give values of 400 mV, 0.9 mA, 0.38 and 1.7% for the open-circuit voltage, V_oc, the short-circuit current, I_sc, the fill factor, FF, and conversion efficiency, η, respectively.     

Low-voltage antimony-doped SnO2 nanowire transparent transistors gated by microporous SiO2-based proton conductors

A battery drivable low-voltage transparent lightly antimony（Sb）-doped SnO2 nanowire electric-double-layer （EDL） field-effect transistor （FET） is fabricated on an ITO glass substrate at room temperature. An ultralow operation voltage of 1 V is obtained on account of an untralarge specific gate capacitance （- 2.14 μF/cm2） directly bound up with mobile ions-induced EDL （sandwiched between the top and bottom electrodes） effect. The transparent FET shows excellent electric characteristics with a field-effect mobility of 54.43 cm2/V. s, current on/off ration of 2 × 104, and subthreshold gate voltage swing （S = dVgs/d（logIds）） of 140 mV/decade. The threshold voltage Yth （0.1 V） is estimated which indicates that the SnO2 namowire transistor operates in an n-type enhanced mode. Such a low-voltage transparent nanowire transistor gated by a microporous SiO2-based solid electrolyte is very promising for battery-powered portable nanoscale sensors.     

Line Positions and Intensities of the ν1+ ν2+ 3ν3, ν2+ 4ν3, and 3ν1+ 2ν2Bands of Ozone

Using a Fourier transform spectrometer, we have recorded the spectra of ozone in the region of 4600 cm⁻¹, with a resolution of 0.008 cm⁻¹. The strongest absorption in this region is due to the ν₁+ ν₂+ 3ν₃band which is in Coriolis interaction with the ν₂+ 4ν₃band. We have been able to assign more than 1700 transitions for these two bands. To correctly reproduce the calculation of energy levels, it has been necessary to introduce the (320) state which strongly perturbs the (113) and (014) states through Coriolis- and Fermi-type resonances. Seventy transitions of the 3ν₁+ 2ν₂band have also been observed. The final fit on 926 energy levels withJ_max= 50 andK_max= 16 gives rms = 3.1 × 10⁻³cm⁻¹and provides a satisfactory agreement of calculated and observed upper levels for most of the transitions. The following values for band centers are derived: ν₀(ν₁+ ν₂+ 3ν₃) = 4658.950 cm⁻¹, ν₀(3ν₁+ 2ν₂) = 4643.821 cm⁻¹, and ν₀(ν₂+ 4ν₃) = 4632.888 cm⁻¹. Line intensities have been measured and fitted, leading to the determination of transition moment parameters for the two bands ν₁+ ν₂+ 3ν₃and ν₂+ 4ν₃. Using these parameters we have obtained the following estimations for the integrated band intensities,S_V(ν₁+ ν₂+ 3ν₃) = 8.84 × 10⁻²²,S_V(ν₂+ 4ν₃) = 1.70 × 10⁻²², andS_V(3ν₁+ 2ν₂) = 0.49 × 10⁻²²cm⁻¹/molecule cm⁻²at 296 K, which correspond to a cutoff of 10⁻²⁶cm⁻¹/molecule cm⁻².     

Calculation of current–voltage characteristics of a Cu (II) complex/n-Si/AuSb Schottky diode

In this study, Cu (II) complex/n-Si structure has been fabricated by forming a thin organic Cu (II) complex film on n-Si wafer. It has been seen that the structure has clearly shown the rectifying behaviour and can be evaluated as a Schottky diode. The contact parameters of the diode such as the barrier height and the ideality factor have been calculated using several methods proposed by different authors from current–voltage (I–V) characteristics of the device. The calculated barrier height and ideality factor values from different methods have shown the consistency of the approaches. The obtained ideality factor which is greater than unity refers the deviation from ideal diode characteristics. This deviation can be attributed to the native interfacial layer in the organic/inorganic interface and the high series resistance of the diode. In addition, the energy distribution of the interface state density (N_ss) in the semiconductor band gap at Cu (II) complex/n-Si interface obtained from I–V characteristics range from 2.15 × 10¹³ cm⁻² eV⁻¹ at (E_c − 0.66) eV to 5.56 × 10¹² cm⁻² eV⁻¹ at (E_c − 0.84) eV.     

The effect of gamma irradiation on electrical and dielectric properties of Al-TiW-Pd2Si/n-Si Schottky diode at room temperature

The effects of ⁶⁰Co (γ-ray) irradiation on the electrical and dielectric properties of Al-TiW-Pd₂Si/n-Si Schottky diodes (SDs) have been investigated by using capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements at room temperature and 500 KHz. The corrected capacitance and conductance values were obtained by eliminating the effect of series resistance (R_s) on the measured capacitance (C_m) and conductance (G_m) values. The high-low frequency capacitance (CHF-CLF) method given in [12] as N_ss = (1/qA) [((1/C_LF) − (1/C_ox))⁻¹ −  ((1/C_HF) − (1/C_ox))⁻¹] was successfully adapted to the before-after irradiation capacitance given in this report as N_ss = (1/qA) [((1/C_bef) − (1/C_ox))⁻¹ − ((1/C_after) − (1/C_ox))⁻¹] for the analyzing the density of interface states. The N_ss-V plots give a distinct peak corresponding to localized interface states regions at metal and semiconductor interface. The experimental values of the ac electrical conductivity (σ_ac), the real (M′) and imaginary (M″) parts of the electrical modulus were found to be strong functions of radiation and applied bias voltage, especially in the depletion and accumulation regions. The changes in the dielectric properties in the depletion and accumulation regions stem especially from the restructuring and reordering of the charges at interface states and surface polarization whereas those in the accumulation region are caused by series resistance effect.     

Investigation of temperature-dependent electrical properties of p-VOPc/n-si heterojunction under dark conditions

An organic/inorganic heterojunction p-VOPc/n-Si was fabricated and its electrical properties were investigated. Temperature-dependent dark current–voltage (I–V) characteristics of the heterojunction exhibited rectification behaviour with a rectification ratio of 405 at ±1 V and room temperature. The current–voltage characteristics of the cell showed ohmic conduction at low voltages followed by a space charge-limited current (SCLC) conduction dominated by an exponential trap distribution at higher voltages. At room temperature, the series and shunt resistances were found to be approximately 1.4 and 100 kΩ, respectively. Diode ideality factor n was found to be 3.2 at room temperature and dropped to 1.9 at 363 K. Room temperature mobility of vanadyl phthalocyanine (VOPc) was extracted from the I–V characteristics in the SCLC region and was found approximately 15.5 × 10⁻³ cm² V⁻¹ s⁻¹. The effective barrier height, Ф_B, was estimated as 0.77 eV. The effect of temperature, on various heterojunction parameters was recorded under dark conditions and at temperatures ranging from 300 to 363 K.     

Conversion of covalent to ionic character of V2O5–CeO2–PbO–B2O3 glasses for solid state ionic devices

xV₂O₅–xCeO₂–(30−x)PbO–(70−x) B₂O₃ glasses are synthesized by using the melt quench technique. The number of studies such as XRD, density, molar volume, optical band gap, refractive index and FTIR spectroscopy are employed to characterize the glasses. The band gap decreases from 2.20 to 1.78 eV and density increases from 3.49 to 4.25 g/cm³. FTIR spectroscopy reveals that incorporation of V₂O₅ in glass network helps to convert the structural units of [BO₃] into [BO₄]. At higher concentration of vanadium, VO vibration of [VO₅] structural units and V–O–V vibration are present. The bond ionicity of glasses increases with incorporation of V₂O₅ contents.     

Ascent of open-circuit voltage on diamond-like carbon photovoltaic cell by infrared heating-assisted pulsed-laser deposition

Phosphorus-doped diamond-like carbon (DLC) films were deposited on quartz and p-type silicon (p-Si) substrates by pulsed-laser deposition. Open-circuit voltage (V _oc) and short-circuit density (I _sc/cm²) from a heating process converted from one type of electrode to another and the two types of electrode pattern are shown by the V–I characteristics. The first heating process was by a ceramic heater, and the other was by an infrared heater. We adopted two electrode patterns, from a bipectinate electrode and a plot pattern electrode, to measure electric photovoltaic characteristics. We were able to upgrade V _oc and I _sc/cm² to 35∼45 mV, and 0.24 μA/cm², respectively, under infrared heating. V _oc by the plot pattern electrode was over 2 V under infrared heating and ceramic heating did not match this on deposition by the PLD method.     

Effects of ZnO coating on the performance of TiO2 nanostructured thin films for dye-sensitized solar cells

ZnO-coated TiO₂ (ZTO) thin films were deposited on ITO substrates by a sol–gel method for application as the work electrode for dye-sensitized solar cells (DSSCs). The I–V curve and the incident photon-to-current conversion efficiency (IPCE) value of DSSCs for ZTO thin films were studied and compared with single TiO₂ films. The results show that the short-circuit photocurrent (J _sc) and open-circuit voltage (V _oc) values increased from 3.7 mA/cm² and 0.68 V for the DSSCs with a single TiO₂ film to 4.5 mA/cm² and 0.72 V, respectively, for the DSSCs with a ZTO thin film. It indicated that the DSSCs with a ZTO thin film contributed to provide an inherent energy barrier that suppressed charge recombination significantly. In addition, the higher IPCE value in the ZTO thin film is attributed to the better charge separation by a fast electron transfer process using two semiconductors with different conduction band edges and energy positions.     

Electrical and interface characteristics of nanocrystalline n-Zn0.5Cd0.5S/p-Cu2S heterojunction structure prepared by dip coating

Nanocrystalline of n-Zn_0.5Cd_0.5S/p-Cu₂S heterojunctions were successfully prepared by the dip coating method. The surface morphology and the composition analysis were made by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) technique, respectively. Temperature dependent current–voltage characteristics of the heterojunctions were measured in the temperature range 300–400 K with a step of 25 K. The current–voltage (I–V) characteristics exhibit electrical rectification behavior. The zero bias barrier height (Φ_B0) and the ideality factor (n) are affected by temperature. Interface states at the n-Zn_0.5Cd_0.5S/p-Cu₂S heterojunction play a crucial role in determining the electrical characteristics of the heterojunction. The high value of n can be ascribed to the presence of an interfacial layer. The energy distribution profile of the density of interface states (N_ss) was extracted from the forward bias I–V measurements using the width of the depletion region deduced from the capacitance -voltage characteristics at high frequency (1MHz).     

The fabrication and characterization of 4H SiC power UMOSFETs

The fabrication of 4H-SiC vertical trench-gate metal-oxide-semiconductor field-effect transistors(UMOSFETs) is reported in this paper.The device has a 15-μm thick drift layer with 3×1015 cm-3 N-type doping concentration and a 3.1μm channel length.The measured on-state source-drain current density is 65.4 A/cm2 at Vg = 40 V and VDS = 15 V.The measured threshold voltage(Vth) is 5.5 V by linear extrapolation from the transfer characteristics.A specific on-resistance(Rsp-on) is 181 mΩ·cm2 at Vg = 40 V and a blocking voltage(BV) is 880 V(IDS = 100 μA@880V) at Vg = 0 V.     

Fourier Transform Infrared Emission Spectroscopy of thebΠ–aΣSystem of BN

The emission spectrum of BN has been investigated in the 1800–9000 cm⁻¹region using a Fourier transform spectrometer. BN was formed in a microwave discharge of He with a trace of BCl₃and N₂. The bands observed in the 3000–7800 cm⁻¹interval have been assigned as theb¹Π–a¹Σ⁺transition, with the 0–0 band at 3513.99040(43) cm⁻¹. This transition is analogous to theA¹Π_u–X¹Σ⁺_g(Phillips) system of the isoelectronic C₂molecule. The rotational analysis of the 0–0, 1–1, 1–0, 2–1, 3–2, 2–0, 3–1, 4–2, and 4–1 bands has been obtained and the molecular constants for theb¹Π anda¹Σ⁺states have been determined. A local perturbation has been observed in thev= 1 vibrational level of theb¹Π state nearJ= 18 caused by the interaction with thev= 3 vibrational level of thea¹Σ⁺state. The principal equilibrium constants for thea¹Σ⁺state are: ω_e= 1705.4032(11) cm⁻¹, ω_ex_e= 10.55338(52) cm⁻¹,B_e= 1.683771(10), α_e= 0.013857(16) cm⁻¹, andr_e= 1.2745081(37) Å. Although theb¹Π–a¹Σ⁺transition has recently been seen in emission from boron nitride trapped in solid neon matrices [J. Chem. Phys.104,3143–3146 (1996)], our work represents the first observation of this transition of BN in the gas phase.     

Rovibrational constants for the ground state and ν8 = 1 state of ethylene-d3 (C2HD3) by high-resolution FTIR spectroscopy

The Fourier transform infrared (FTIR) spectrum of the ν₈ fundamental band of ethylene-d₃ (C₂HD₃) was recorded with a unapodized resolution of 0.0063 cm⁻¹ in the wavenumber region of 840–980 cm⁻¹. By assigning and fitting a total of 738 infrared transitions using a Watson’s A-reduced Hamiltonian in the I^r representation, rovibrational constants for the upper state (ν₈ = 1) up to all five quartic centrifugal distortion terms were derived for the first time. The root-mean-square (rms) deviation of the fit was 0.00076 cm⁻¹. The ground state rovibrational constants of C₂HD₃ were also determined for the first time by a fit of 450 combination-differences from the present infrared measurements, with rms deviation of 0.00075 cm⁻¹. Local frequency perturbations were not detected in the C-type ν₈ band of C₂HD₃ which is centred at 918.73199 ± 0.00007 cm⁻¹.     

Photocarrier injection and the I-V characteristics of La0.8Sr0.2MnO3/SrTiO3:Nb heterojunctions

Oxide heterojunctions made of p-type La_0.8Sr_0.2MnO₃ (LSMO) and niobium-doped n-type SrTiO₃ (STO:Nb) have been fabricated by the pulsed laser deposition (PLD) technique and characterized under UV light irradiation by measuring the current-voltage, photovoltaic properties and the junction capacitance. It is shown that the heterojunctions work as an efficient UV photodiode, in which photogenerated holes in the STO:Nb substrate are injected to the LSMO film. The maximum surface hole density Q/e and external quantum efficiency γ are estimated to be 8.3×10¹² cm⁻² and 11% at room temperature, respectively. They are improved significantly in a p-i-n junction of LSMO/STO/STO:Nb, where Q/e and γ are 3.0×10¹³ cm⁻² and 27%, respectively.     

Electronic energy levels of lithium gadolinium tetraphosphate (LiGdP4O12)

The positions of 15 electronic energy levels above the ground level ⁸S_7/2 of Gd³⁺ in flux-grown single crystals of LiGdP₄O₁₂ have been determined from 4f–4f transitions observed in absorption spectra in the range 190–340 nm at T = 293 K. The experimental energy levels have been compared with theoretical ones obtained by two parameters, F₂ = 392 cm⁻¹ and ζ_4f = 1525 cm⁻¹, in the intermediate coupling approximation.     

High-Resolution Infrared Studies of ν1, 2ν1, and 2ν4 Bands of CHCl3

The C-H stretching fundamental band ν₁ (3033 cm⁻¹) of chloroform CH³⁵Cl₃ has been investigated together with the first overtone 2ν₁ (5941 cm⁻¹) in order to determine the rotation vibration parameters. From the ν₁ band α₁^C=−0.025 46(41)×10⁻³ cm⁻¹ and α₁^B=−0.010 688(44)×10⁻³ cm⁻¹ were obtained. The hot bands connected to the low lying fundamentals ν₃ and ν₆ have been analyzed and anharmonicity constants have been derived. Both the parallel and the perpendicular component band of the C-H bending overtone 2ν₄ have also been studied. In the parallel band (2410 cm⁻¹) more than 900 lines were included in the fit. In the perpendicular band (2443 cm⁻¹) 2615 lines were fitted using a model with one resonance. Among other things the results C₀−C_v=0.025 262 (20)×10⁻³ cm⁻¹, B₀−B_v=0.134 883 (25)×10⁻³ cm⁻¹, and (Cζ)_v=−0.111 867 56 (30) cm⁻¹ were obtained.     

Fabrication and characterization of 4H—SiC bipolar junction transistor with double base epilayer

In this paper we report on a novel structure of a 4H-SiC bipolar junction transistor with a double base epilayer that is continuously grown.The measured dc common-emitter current gain is 16.8 at IC = 28.6 mA(J C = 183.4 A/cm2),and it increases with the collector current density increasing.The specific on-state resistance(Rsp-on) is32.3mΩ·cm 2 and the open-base breakdown voltage reaches 410 V.The emitter N-type specific contact resistance and N + emitter layer sheet resistance are 1.7×10-3 Ω·cm2 and 150 /,respectively.     

Co-reduction synthesis of new LnxSb2−xS3 (Ln: Nd, Lu, Ho) nanomaterials and investigation of their physical properties

New Ln_xSb_2−xS₃ (Ln: Lu³⁺, Ho³⁺, Nd³⁺)-based nanomaterials were synthesized by a co-reduction method. Powder XRD patterns indicate that the Ln_xSb_2−xS₃ crystals (Ln=Lu³⁺, Ho³⁺, x=0.00−0.1 and Ln=Nd³⁺, x=0.00−0.08) are isostructural with Sb₂S₃. SEM images show that doping of Lu³⁺ and Ho³⁺ ions in the lattice of Sb₂S₃ results in nanorods while that in Nd³⁺ leads to nanoflowers. UV-vis absorption and emission spectroscopy reveal mainly electronic transitions of the Ln³⁺ ions in case of Ho³⁺ and Nd³⁺ doped nanomaterials. Emission spectra show intense transitions from excited to ground state of Ln³⁺. Emission spectra of doped materials, in addition to the characteristic red emission peaks of Sb₂S₃, show other emission bands originating from f-f transitions of the Ho³⁺ ions. TGA curves indicated that Sb₂S₃ has the highest thermal stability. The electrical conductance of Ln-doped Sb₂S₃ is higher than undoped Sb₂S₃, and increase with temperature.     

Simple solar cells of 3.5% efficiency with antimony sulfide‐selenide thin films

Thin films of antimony sulfide‐selenide solid solutions (Sb₂S_x Se_3–x) were prepared by chemical bath deposition and thermal evaporation to constitute solar cells of a transparent conductive oxide (FTO)/CdS/Sb₂S_x Se_3–x/C–Ag. The cell parameters vary depending on the sulfide‐selenide composition in the films. The best solar cell efficiency of 3.6% was obtained with a solid solution Sb₂S_1.5Se_1.5 prepared by thermal evaporation of the precipitate for which the open circuit voltage is 0.52 V and short circuit current density, 15.7 mA/cm²under AM 1.5G (1000 W/m²) solar radiation. For all‐chemically deposited solar cells of Sb₂S_1.1Se_1.9 absorber, these values are: 2.7%, 0.44 V, and 15.8 mA/cm², and for Sb₂S_0.8Se_2.2, they are: 2.5%, 0.38 V and 18 mA/cm². (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Current transport mechanism in Al/Si3N4/p-Si (MIS) Schottky barrier diodes at low temperatures

The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of metal-insulator-semiconductor (Al/Si₃N₄/p-Si) Schottky barrier diodes (SBDs) were measured in the temperature range of 80-300 K. By using the thermionic emission (TE) theory, the zero-bias barrier height Φ_B0 calculated from I-V characteristics was found to increase with increasing temperature. Such temperature dependence is an obvious disagreement with the negative temperature coefficient of the barrier height calculated from C-V characteristics. Also, the ideality factor decreases with increasing temperature, and especially the activation energy plot is nonlinear at low temperatures. Such behaviour is attributed to Schottky barrier inhomogeneties by assuming a Gaussian distribution of barrier heights (BHs) at interface. We attempted to draw a Φ_B0 versus q/2kT plot to obtain evidence of a Gaussian distribution of the BHs, and the values of Φ_Bo = 0.826 eV and α_o = 0.091 V for the mean barrier height and standard deviation at zero-bias, respectively, have been obtained from this plot. Thus, a modified ln(I_o/T²) − q²σ_o²/2(kT)² versus q/kT plot gives Φ_B0 and Richardson constant A^* as 0.820 eV and 30.273 A/cm² K², respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 30.273 A/cm² K² is very close to the theoretical value of 32 A/cm² K² for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/Si₃N₄/p-Si Schottky barrier diodes can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights. In addition, the temperature dependence of energy distribution of interface state density (N_SS) profiles was determined from the forward I-V measurements by taking into account the bias dependence of the effective barrier height and ideality factor.