Showing papers in "Solid-state Electronics in 2003"
TL;DR: In this article, the authors report on the contact resistances for pentacene thin film transistors with two different designs: top and bottom contact configurations (referred to as TC and BC TFTs, respectively) for two different contact metals (gold and palladium).
Abstract: We report on the contact resistances for pentacene thin film transistors with two different designs: top and bottom contact configurations (referred to as TC and BC TFTs, respectively) for two different contact metals (gold and palladium). The extraction was done based on the dependencies of the channel resistances on the gate length and gate voltage. The extracted gold TC TFT contact resistance depends on VGS, but shows no dependence on the drain bias. The TC TFT contact resistance is comparable to or exceeds the channel resistance for channels shorter than approximately 10 μm. The contact resistance of BC TFTs depends both on gate and drain bias. We propose a circuit simulating the BC TFT contact resistance and verify the circuit applicability by extracting and comparing the TFT channel resistances at different drain voltages. Our results reveal an important role played by contact resistances and provide an accurate model of the contact phenomena suitable for implementation in Spice or other circuit simulators.
312 citations
TL;DR: In this article, a simple analytical approximation has been obtained to describe the temperature and concentration dependencies of the low-field mobility in gallium nitride (GaN) in wide temperature (50⩽ T ⩽1000 K) and concentration (10 14 N 10 19 cm −3 ) ranges.
Abstract: Simple analytical approximation has been obtained to describe the temperature and concentration dependencies of the low-field mobility in gallium nitride (GaN) in wide temperature (50⩽ T ⩽1000 K) and concentration (10 14 ⩽ N ⩽10 19 cm −3 ) ranges. The dependence of the temperature T m at which the mobility μ is at a maximum on the doping level is also obtained. Results obtained can be directly used for computer simulation of GaN-based devices.
220 citations
TL;DR: In this article, an inkjet printed all-polymer capacitor has been demonstrated, analogous to that of the common parallel plate capacitor, and the electrical characteristics of the polymer capacitor are discussed in detail.
Abstract: All-polymer capacitors have been fabricated only by the inkjet printing technique. A conductive polymer, poly(3,4-ethylenedioxythiophene), has been employed as the electrode material of the capacitor. A precursor-route polyimide was applied as the insulator of the device. The fabrication process of the inkjet printed all-polymer capacitor has been demonstrated. The electrical characteristics of the polymer capacitor, analogous to that of the common parallel plate capacitor, are discussed in detail. The all-polymer capacitor has been applied to the polymer RC filter circuits. The characteristics of the inkjet printed polymer RC filter are also demonstrated.
205 citations
TL;DR: In this paper, the effect of the interfacial oxide layer and the ideality factor n in the current transport mechanism of MIS diodes was investigated and the energy distribution of Nss was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height.
Abstract: In order to good interpret the experimentally observed non-ideal Al/SnO2/p-Si (MIS) Schottky diode parameters such as the barrier height ΦB, series resistance Rs and density of interface states Nss, a calculation method has been reported by taking into account interfacial oxide layer and ideality factor n in the current transport mechanism. The current–voltage (I–V) and capacitance–voltage (C–V) characteristics of MIS diodes are studied over a wide temperature range of 80–350 K. The effects of Rs, interfacial layer and Nss on I–V and C–V characteristics are investigated. The values of n were strongly temperature dependent and decreased with increasing temperature. The energy distribution of Nss was determined from the forward bias I–V characteristics by taking into account the bias dependence of the effective barrier height. The mean Nss estimated from I–V and C–V measurements decreased with increasing temperature. The Rs estimated from Cheung’s functions was strongly temperature dependent and decreased with increasing temperature. The I–V characteristics confirmed that the distribution of Nss, Rs and interfacial layer are important parameters that influence the electrical characteristics of MIS devices.
195 citations
TL;DR: In this paper, a review of recent advancements of transparent oxide semiconductors (TOS) toward new frontiers of oxide electronics are reviewed based on their efforts, categorized as novel functional materials, heteroepitaxial growth techniques, and device fabrications.
Abstract: Recent advancements of transparent oxide semiconductors (TOS) toward new frontiers of “oxide electronics” are reviewed based on our efforts, categorized as “novel functional materials”, “heteroepitaxial growth techniques”, and “device fabrications”. Topics focused in this paper are: (1) highly conductive ITO thin film with atomically flat surface, (2) p-type TOS material ZnRh2O4, (3) deep-ultraviolet (DUV) transparent conductive oxide β-Ga2O3 thin film, (4) electrochromic oxyfuolide NbO2F, (5) single-crystalline films of InGaO3(ZnO)m grown by reactive solid-phase epitaxy, (6) p-type semiconductor LaCuOS/Se epitaxial films capable of emitting UV- and purple-light, (7) p–n homojunction based on bipolar CuInO2, (8) transparent FET based on single-crystalline InGaO3(ZnO)5 films, and (9) UV-light emitting diode based on p–n heterojunction.
144 citations
TL;DR: In this article, a consistent set of epitaxial, n-type conducting ZnO thin films, nominally undoped, doped with Ga or Al, or alloyed with Mg or Cd, was grown by pulsed laser deposition (PLD) on single-crystalline c-plane sapphire (0, 0,0,1) substrates, and characterized by Hall measurement, and UV/VIS optical transmission spectroscopy.
Abstract: A consistent set of epitaxial, n-type conducting ZnO thin films, nominally undoped, doped with Ga or Al, or alloyed with Mg or Cd, was grown by pulsed laser deposition (PLD) on single-crystalline c-plane sapphire (0 0 0 1) substrates, and characterized by Hall measurement, and UV/VIS optical transmission spectroscopy. The optical band gap of undoped ZnO films at nearly 3.28 eV was shifted by alloying with Mg up to 4.5 eV and by alloying with Cd down to 3.18 eV, dependent on the alloy composition. In addition, highly doped ZnO:Al films show a blue-shifted optical absorption edge due to filling of electronic states in the conduction band. The Hall transport data of the PLD (Mg,Zn,Cd)O:(Ga,Al) thin films span a carrier concentration range of six orders of magnitude from 3 × 1014 to 3 × 1020 cm−3, which corresponds to a resistivity from 5 × 10−4 to 3 × 103 Ω cm. Structurally optimized, nominally undoped ZnO films grown with ZnO nucleation and top layer reached an electron mobility of 155 cm2/V s (300 K), which is among the largest values reported for heteroepitaxial ZnO thin films so far. Finally, we succeeded in combining the low resistivity of ZnO:Ga and the band gap shift of MgZnO in MgZnO:Ga thin films. This results demonstrate the unique tunability of the optical and electrical properties of the ZnO-based wide-band gap material for future electronic devices.
137 citations
TL;DR: In this article, the implications of inversion charge linearization in compact MOS transistor modeling are discussed, and an improvement to the EKV charge-based model is proposed in the form of a more accurate charge-voltage relationship.
Abstract: In this paper, the implications of inversion charge linearization in compact MOS transistor modeling are discussed. The charge-sheet model provides the basic relation among inversion charge and applied potentials, via the implicit surface potential. A rigorous derivation of simpler relations among inversion charge and applied external potentials is provided, using the technique of inversion charge linearization versus surface potential. The new concept of the pinch-off surface potential and a new definition of the inversion charge linearization factor are introduced. In particular, we show that the EKV charge-based model can be considered as an approximation to the more general approach presented here. An improvement to the EKV charge-based model is proposed in the form of a more accurate charge–voltage relationship. This model is analyzed in detail and shows an excellent agreement with the charge sheet model. The normalization of voltages, current and charges, as motivated by the inversion charge linearization, results in a major simplification in compact modeling in static as well as non-quasi-static derivations.
131 citations
TL;DR: In this article, the first all-polymer RC filter circuits by all-inkjet printing technology are fabricated for the first time using conductive polymers such as polyaniline and poly(3, 4-ethylenedioxythiophene) have been used as the electrode material of the capacitor as well as the resistor material.
Abstract: All-polymer RC filter circuits by all-inkjet printing technology are fabricated for the first time. Conductive polymers such as polyaniline and poly(3, 4-ethylenedioxythiophene) have been used as the electrode material of the capacitor as well as the resistor material. The fabrication process and the characteristics of the printed capacitor and RC filter have been demonstrated. Simulation of the printed RC circuit has been demonstrated and compared with the experimental measurement results. A detail discussion has been given about the all-polymer capacitor and RC filter.
122 citations
TL;DR: In this article, the optical and electrical properties of indium tin oxide (ITO), Ni(3.5 nm)/ITO(60 nm) and Ni( 5 nm)/Au(5 nm) films were studied, and it was found that the normalized transmittance of ITO and Ni/ITO films could reach 98.2% and 86.6% at 470 nm, respectively.
Abstract: The optical and electrical properties of indium tin oxide (ITO)(60 nm), Ni(3.5 nm)/ITO(60 nm) and Ni(5 nm)/Au(5 nm) films were studied. It was found that the normalized transmittance of ITO and Ni/ITO films could reach 98.2% and 86.6% at 470 nm, which was much larger than that of the Ni/Au film. It was also found that both Ni/ITO and Ni/Au could form good ohmic contact on top of p-GaN. In contrast, ITO on p-GaN was electrically poor and non-ohmic. Nitride-based light-emitting diodes (LEDs) with these three p-contact layers were also fabricated. It was found that the LED forward voltage was 3.65, 3.26 and 3.24 V for the LEDs with ITO, Ni/ITO and Ni/Au p-contact layer, respectively. With a 20 mA current injection, it was also found that measured output power was 7.50, 6.59 and 5.26 mW for the LEDs with ITO, Ni/ITO and Ni/Au p-contact layer, respectively. Although the LED with ITO p-contact could provide the largest output intensity, its lifetime was the shortest due to severe heating effect.
115 citations
TL;DR: In this paper, Nitride-based blue LEDs prepared on both patterned and conventional sapphire substrates were both fabricated and the peak positions of these two LEDs were about the same.
Abstract: Nitride-based blue LEDs prepared on both patterned and conventional sapphire substrates were both fabricated It was found that although the EL peak positions of these two LEDs were about the same, the EL intensity of LED grown on patterned sapphire substrate was about 35% larger The maximum output power of LED grown on patterned sapphire substrate also occurred at higher injection current The reliability of LED grown on patterned sapphire substrate was also found to be better There improvements could all be attributed to the reduced dislocation density in the LEDs grown on patterned sapphire substrates
102 citations
TL;DR: In this paper, an exact analytical solution of the channel surface potential as an explicit function of the gate voltage for either n or p channel operation is presented, and an approximate but highly accurate analytical solution is continuously valid for all regions of operation.
Abstract: Two useful applications of the Lambert W function to undoped-body MOSFET modeling are presented. Firstly, it is applied to the problem of inverting the gate voltage versus channel surface potential equation. The result is an exact analytical solution of the channel surface potential as an explicit function of the gate voltage for either n or p channel operation. Additionally an approximate but highly accurate analytical solution is presented which is continuously valid for all regions of operation. Secondly, we propose a new unambiguous analytical definition for the threshold voltage of these undoped-body devices. This definition overcomes the impossibility of using the traditional definition based on the bulk Fermi potential, and the ambiguities introduced by other definitions. The threshold voltage is mathematically described also using the Lambert W function at the transition point from subthreshold to superthreshold behavior. An approximation for the )1 branch of the Lambert W function is proposed to express the threshold voltage approximately using elementary logarithmic functions. These new descriptions are then verified against two-dimensional numerical device simulations. 2003 Elsevier Ltd. All rights reserved.
TL;DR: In this article, single crystals of Sn-doped ZnO were implanted with Co or Mn at doses designed to produce transition metal concentrations of 3-5% in the near surface.
Abstract: Bulk single crystals of Sn-doped ZnO were implanted with Co or Mn at doses designed to produce transition metal concentrations of 3–5 at.% in the near-surface (� 2000 A region. The implantation was performed at � 350 Ct o promote dynamic annealing of ion-induced damage. Following annealing at 700 C, temperature-dependent magnetization measurements showed ordering temperatures of � 300 K for Co- and � 250 K for Mn-implanted ZnO. Clear hysteresis loops were obtained at these temperatures. The coercive fields were 6 100 Oe for all measurement temperatures. X-ray diffraction showed no detectable second phases in the Mn-implanted material. One plausible origin for the ferromagnetism in this case is a carrier-induced mechanism. By sharp contrast, the Co-implanted material showed evidence for the presence of Co precipitates with hexagonal symmetry, which is the cause of the room temperature ferromagnetism. Our results are consistent with the stabilization of ferromagnetic states by electron doping in transition metal-doped ZnO predicted by Sato and Katayama–Yoshida [Jpn. J. Appl. Phys. 40 (2001) L334]. This work shows the excellent promise of Mn-doped ZnO for potential room temperature spintronic applications. 2003 Elsevier Ltd. All rights reserved.
TL;DR: In this paper, a new type of supply clamp is proposed for reducing the parasitic capacitance in ESD protection structures, and the approach and physics of the new supply clamp are discussed, and both experimental data and device simulation are provided in support of the investigation.
Abstract: On-chip electrostatic discharge (ESD) protection structures are frequently used in microchips to protect the core circuit again ESD damages. Relatively large parasitic capacitances associated with these structures, however, can degrade the performance of microchips. In this paper, a new type of supply clamp is studied for the purpose of reducing the parasitic capacitance in ESD protection structures. The approach and physics of the new supply clamp are discussed, and both experimental data and device simulation are provided in support of the investigation.
IBM1
TL;DR: Strain-induced enhancement of current drive is a promising way to extend the advancement of CMOS performance as mentioned in this paper and has been demonstrated with key elements of modern day's CMOS technology.
Abstract: Strain-induced enhancement of current drive is a promising way to extend the advancement of CMOS performance. Fabrication of strained Si MOSFET has been demonstrated with key elements of modern day’s CMOS technology. Significant mobility and current drive enhancements were observed. Recent advancements in the SS devices are summarized, and the challenges in device physics/design issues as well as in materials/process integration are highlighted.
TL;DR: In this article, the authors compared simulated write/erase characteristics of nonvolatile memory with different oxides SiO 2, Al 2 O 3 and ZrO 2 as a top dielectric.
Abstract: The comparison of simulated write/erase characteristics of silicon–oxide–nitride–oxide–silicon (SONOS) nonvolatile memory with different oxides SiO 2 , Al 2 O 3 and ZrO 2 as a top dielectric was made. We demonstrate, that an application of high- k dielectrics allows to decrease the write/erase programming voltage amplitude or programming time from 1 ms to 10 μs. The ZrO 2 suppresses parasitic electron injection from polysilicon gate. Also the design of SONOS memory based on high- k dielectrics is promising for terabit scale using hot carriers injection EEPROM and DRAM memory.
TL;DR: In this article, single walled carbon nanotubes (SWCNTs) have been aligned across the metal electrodes using a dc electric field, and an improved dispersion of CNTs has been found in dimethylformamide solution compared to ethanol.
Abstract: Single walled carbon nanotubes (SWCNTs) have been aligned across the metal electrodes using a dc electric field. Effects of electric field strength, nanotube concentration in the suspension, and the solvents used for CNT dispersion were examined on the aligning nature of nanotubes. An improved dispersion of CNTs has been found in dimethylformamide solution compared to ethanol. CNTs mostly moved towards anode for the applied electric field indicating the negative charge of the nanotubes. Experimental results exhibit the possibilities of precise positioning of nanotubes on pre-patterned electrodes by controlling the magnitude of electric field as well as the concentration of CNT suspension.
TL;DR: In this article, a fully microscopic model is used to calculate absorption/gain and spontaneous emission for GaInNAs quantum-well laser gain media, which can be used to derive the optical properties for the regime of semiconductor laser operation from low density photo luminescence spectra.
Abstract: A fully microscopic model is used to calculate absorption/gain and spontaneous emission for GaInNAs quantum-well laser gain media. It is demonstrated how this approach can be used to derive the optical properties for the regime of semiconductor laser operation from low density photo luminescence spectra which can be obtained from simple experiments. Numerical results are presented showing that increased well depth leads to strongly increased differential gains and gain amplitudes and pronounced shifts of the gain maximum with increasing density. On the basis of a quantum Blotzmann model for the incoherent carrier dynamics it is shown, that high carrier confinement can lead to unusually long carrier capture times. Furthermore, temperature dependent bandstructure parameters for GaInNAs for the applied 10-band k · p -model are presented that have been derived from comparison to recent experimental data.
TL;DR: In this article, the authors describe scaling considerations and process optimization to achieve lowvoltage operation (+7 V write for 2.5 ms/−7 V erase for 7.5ms) with 10-year retention at 150 °C.
Abstract: We present results on scaled silicon–oxide–nitride–oxide–silicon (SONOS) nonvolatile semiconductor memory devices with oxygen-rich ‘oxynitride’ charge storage layers. SONOS devices are designed specifically for high-density EEPROMs operating at high temperatures. We describe scaling considerations and process optimization to achieve low-voltage operation (+7 V write for 2.5 ms/−7 V erase for 7.5 ms) with 10-year retention at 150 °C. Memory transistors are programmed, erased, and read at elevated temperatures in order to observe thermal excitation of electrons from traps in oxynitride charge storage layers. The density of traps in the oxynitride is extracted using charge decay rates of programmed transistors at elevated temperatures. Trap density profiles for oxynitride films are compared with trap density profiles for silicon-rich nitride films.
TL;DR: In this article, an AlGaN/GaN heterojunction field effect transistor (HFET) with a very low on-state resistance was fabricated on a sapphire substrate using gas-source molecular beam epitaxy.
Abstract: We fabricated an AlGaN/GaN heterojunction field effect transistor (HFET) with a very low on-state resistance. An undoped Al0.2Ga0.8N(30 nm)/GaN(2 μm) heterostructure was grown on a sapphire substrate using gas-source molecular-beam epitaxy. The undoped GaN layer had a high resistivity (above 10 M Ω ) and the breakdown field of the undoped layer was about 2 MV/cm. Si-doped GaN with a carrier concentration of 5×1019 cm−3 was selectively grown in the source and drain regions for obtaining a very low contact resistance. As a result, a very low ohmic below 1×10−7 Ω cm2 was obtained. After that, an Al0.2Ga0.8N/GaN HFET was fabricated. The gate width was 20 cm and the gate length was 2 μm. The ohmic electrode materials were Al/Ti/Au and the Schottky electrodes were Pt/Au. The distance between the source and the drain was 13 μm. The HFET was operated at a current of over 20 A. A higher switching speed of HFET was obtained.
TL;DR: In this paper, Mn-activated Y2O3-based oxide phosphors are presented as a host material for electroluminescent (TFEL) devices, and shown to have high luminance and luminous efficiencies comparable to those of TFEL devices using ZnS:Mn sulfide phosphor.
Abstract: This report reviews newly developed oxide phosphors shown to be promising as the emitting layer of thin-film electroluminescent (TFEL) devices. Since the first report of a high-luminance TFEL device using a Mn-activated Zn2SiO4 (Zn2SiO4:Mn) phosphor, high-luminance multicolor-emitting TFEL devices have been fabricated using various oxide phosphors activated with Eu or Mn. In addition, many oxides that consist of binary and ternary compounds and multicomponent oxides have been developed and shown to be promising as a host material for TFEL phosphors. This report focuses on Mn-activated Y2O3-based oxide phosphors: a binary compound and various ternary compounds and multicomponent oxides, composed of Y2O3 in combination with another binary compound such as Ga2O3 or GeO2. TFEL devices of which every constituent was an oxide material were fabricated using oxide phosphor thin films deposited by r.f. magnetron sputtering, pulsed laser deposition or a sol–gel process. High luminances and luminous efficiencies comparable to those of TFEL devices using ZnS:Mn sulfide phosphor were realized using Mn-activated Y2O3-based oxide phosphors. Luminances above 7000 cd/m2 (1 kHz-driving voltage) and luminous efficiencies of approximately 10 lm/W (60 Hz driving voltage) were obtained in yellow emitting TFEL devices fabricated using a Y2O3:Mn, a ((Y2O3)0.6–(GeO2)0.4):Mn or a ((Y2O3)0.5–(Ga2O3)0.5):Mn thin film and driven by an ac sinusoidal wave voltage. Also, a high luminance above 1000 cd/m2 for green emission was obtained in a ((Y2O3)0.3–(Ga2O3)0.7):Mn TFEL device driven at 1 kHz.
TL;DR: In this article, loss mechanisms for microstrip and coplanar transmission lines on lossy silicon substrates are analyzed and it is shown that depending on the quality of the silicon/oxide interface the losses can be strongly influenced by the applied bias.
Abstract: Loss mechanisms for microstrip and coplanar transmission lines on lossy silicon substrates are analyzed. It is shown that depending on the quality of the silicon/oxide interface the losses can be strongly influenced by the applied bias. It is also proven that MS losses are much less sensitive to the line DC condition than CPW lines. This is supported both by experimental results and numerical simulations. A continuous analysis of the losses is performed from accumulation to strong inversion and we attribute the observed effects to changes in the carrier static distribution underneath the oxide. It is concluded that neglecting the variations of RF losses vs DC bias conditions can lead to important inaccuracies on the extracted values of circuit and device physical parameters. (C) 2003 Elsevier Ltd. All rights reserved.
TL;DR: In this paper, defect doping of the anatase polymorph that is epitaxial stabilized on (0,0,1) LaAlO 3 was explored using either oxygen or water vapor as the oxidizing species.
Abstract: The synthesis of semiconducting TiO 2 thin films deposited by reactive sputtering is discussed. In particular, defect doping of the anatase polymorph that is epitaxial stabilized on (0 0 1) LaAlO 3 was explored using either oxygen or water vapor as the oxidizing species. For films grown in oxygen, a transition from insulating to metallic conductivity of the films is observed as the O 2 pressure is reduced. X-ray diffraction measurements show the presence of the Ti n O 2 n −1 phase when the oxygen pressure is reduced sufficiently to induce conductive behavior. Hall measurements indicate that these materials are p-type. In contrast, the use of water vapor as the oxidizing species enabled the formation of n-type semiconducting TiO 2 with carrier density on the order of 10 18 cm −3 and mobility of 10–15 cm 2 /V s.
TL;DR: In this article, a 2D simulation code resolving the Schrodinger and Poisson equations coupled with the ballistic transport equation in double-gate (DG) devices has been developed, which includes the quantum mechanical tunneling of carriers through the source-to-drain barrier and the wave function penetration in the gate oxide.
Abstract: A new 2-D simulation code resolving the Schrodinger and Poisson equations coupled with the ballistic transport equation in double-gate (DG) devices has been developed. The present approach also includes the quantum mechanical tunneling of carriers through the source-to-drain barrier and the wave function penetration in the gate oxide. This code has been used to investigate the operation of DG SOI MOSFETs in the deca–nanometer range (5–20 nm) with ultra-thin gate oxide and film bodies (1.5 nm). The present study particularly emphasizes on the impact of quantum tunneling on the DG SOI MOSFET scaling in terms of short-channel effects, off-state current and subthreshold slope.
TL;DR: A modified Norde function combined with conventional forward I-V method was used to extract the parameters including barrier height, rectification ratio, ideality factor, as well as the series resistance as mentioned in this paper.
Abstract: Metal/polymer Schottky diodes have been fabricated using spin-coated poly(3,4-ethylenedioxythiophene) (PEDT) doped with poly(styrenesulfonate) (PSS) as the p-type semiconductor and aluminum as the metal. The current–voltage and capacitance–voltage characteristics have been studied at room temperature. The breakdown voltage and rectification ratio of the Al/PEDT Schottky diode are about 5.5 V and 1.3×10 4 , respectively. A modified Norde function combined with conventional forward I – V method was used to extract the parameters including barrier height, rectification ratio, ideality factor, as well as the series resistance. This new method allows extraction of device characteristics from measured I – V curve that deviates from ideal I – V curve caused by series resistance.
TL;DR: In this article, different approaches to the design of a temperature-insensitive quantum dot (QD) laser are proposed, including tunneling injection of carriers into the QDs or by band-gap engineering.
Abstract: Different approaches to the design of a genuinely temperature-insensitive quantum dot (QD) laser are proposed. Suppression of the parasitic recombination outside the QDs, which is the dominant source of the temperature dependence of the threshold current in the conventional design of a QD laser, is accomplished either by tunneling injection of carriers into the QDs or by band-gap engineering. Elimination of this recombination channel alone enhances the characteristic temperatures T0 above 1000 K. Remaining sources of temperature dependence (recombination from higher QD levels, inhomogeneous line broadening, and violation of charge neutrality in QDs) are studied. Tunnelinginjection structures are shown to offer an additional advantage of suppressed effects of inhomogeneous broadening and neutrality violation. 2002 Elsevier Science Ltd. All rights reserved.
TL;DR: The properties of Mn-doped Cu2O are described in this paper, where the epitaxial films were grown by pulsed-laser deposition and X-ray diffraction was used to determine film crystallinity and to address the formation of secondary phases.
Abstract: Semiconducting oxides offer the potential for exploring and understanding spin-based functionality in a semiconducting host material. Theoretical predictions suggest that carrier-mediated ferromagnetism should be favored for p-type material. Cu2O is a p-type, direct wide bandgap oxide semiconductor that may hold interest in exploring spin behavior. In this paper, the properties of Mn-doped Cu2O are described. Activities focused on understanding Mn incorporation during thin-film synthesis, as well as magnetic characterization. The epitaxial films were grown by pulsed-laser deposition. X-ray diffraction was used to determine film crystallinity and to address the formation of secondary phases. SQUID magnetometry was employed to characterize the magnetic properties. Ferromagnetism is observed in selected Mn-doped Cu2O films, but appears to be associated with Mn3O4 secondary phases. In phase-pure Mn-doped Cu2O films, no evidence for ferromagnetism is observed.
TL;DR: In this paper, Nakayama et al. showed that the implantation of Co or Mn into single-crystal BaTiO3, SrTiO 3, or KTaO3(Ca), followed by annealing at 700 � C, produced ferromagnetic behavior over a broad range of transition metal concentrations.
Abstract: Implantation of Co or Mn into single-crystal BaTiO3(K), SrTiO3 or KTaO3(Ca), followed by annealing at 700 � C, produced ferromagnetic behavior over a broad range of transition metal concentrations. For BaTiO3, both Co and Mn implantation produced magnetic ordering temperatures near 300 K with coercivities 670 Oe. The M–T plots showed either a near-linear decrease of magnetization with increasing temperature for Co and a non-Brillouin shaped curve for Mn. No secondary phases were detected by high-resolution X-ray diffraction. The same basic trends were observed for both SrTiO3 and KTaO3, with the exception that at high Mn concentrations (� 5 at.%) the SrTiO3 was no longer ferromagnetic. Our results are consistent with recent reports of room temperature ferromagnetism in other perovskite systems (e.g. LaBaMnO3) and theoretical predictions for transition metal doping of BaTiO3 [Nakayama et al., Jap. J. Appl. Phys. 40 (2001) L1355].
TL;DR: In this paper, a combination of molecular beam epitaxy and a nitrogen plasma source was used to increase the response wavelength of InSb1−xNx with up to 10% nitrogen.
Abstract: Indium antimonide (InSb) has the smallest energy gap of any of the binary III–V materials, leading to a cut-off wavelength of 7 μm at 300 K. The addition of small proportions of nitrogen to InSb offers the prospect of extending the response wavelength into the 8–12 μm range, which is important for thermal imaging in that atmospheric transmission window and because it encompasses the absorption lines of several environmentally important gases and can therefore be used for monitoring the gases. We report on the growth, by a combination of molecular beam epitaxy and a nitrogen plasma source, of InSb1−xNx with up to 10% nitrogen. Structural characterisation techniques of TEM, AFM and SIMS have enabled some optimisation of material quality to be demonstrated by biasing the sample during growth. Measurements on light emitting diodes comprising a superlattice of InSb0.945N0.055/InSb show an emission wavelength of 10.5 μm, which is confirmed by free electron laser assessment. Comparison with first principles band-structure calculations indicate that approximately 10% of the nitrogen is active. Hall effect measurements of 1 μm thick bulk layers indicate an increasing n-type behaviour, the degeneracy effects of which mean, however, that this is only a lower limit.
TL;DR: In this paper, the extent and significance of thermal nonequilibrium is determined from phonon temperature distributions obtained using a common electronic solution and three different heating models (Joule heating, electron/lattice scattering, phonon scattering).
Abstract: The present work considers electrothermal simulation of LDMOS devices and associated nonequilibrium effects. Simulations have been performed on three kinds of LDMOS: bulk Si, partial SOI and full SOI. Differences between equilibrium and nonequilibrium modeling approaches are examined. The extent and significance of thermal nonequilibrium is determined from phonon temperature distributions obtained using a common electronic solution and three different heating models (Joule heating, electron/lattice scattering, phonon scattering). The results indicate that, under similar operating conditions, nonequilibrium behavior is more significant in the case of full SOI devices, where the extent of nonequilibrium is estimated to be twice that of the partial SOI device and four times that of the bulk device. Time development of acoustic phonon and lattice temperatures in the electrically active region indicates that nonequilibrium effects are significant for times less than 10 ns.
TL;DR: The structure of interfaces in superconducting/ferromagnetic YBa2Cu3O7−x/La 0.67Ca 0.33MnO3 superlattices has been analyzed by scanning transmission electron microscopy and high spatial resolution electron energy loss spectroscopy.
Abstract: The structure of interfaces in superconducting/ferromagnetic YBa2Cu3O7−x/La0.67Ca0.33MnO3 superlattices has been analyzed by scanning transmission electron microscopy and high spatial resolution electron energy loss spectroscopy. Individual layers are flat over long lateral distances. The interfaces are coherent, free of defects, exhibiting no roughness, and are located at the BaO plane of the superconductor. Concerning chemical disorder, EELS measurements show the absence of measurable chemical interdiffusion within experimental error bars.