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Lateral memristors consisting of planar Ag electrodes (with sub-micrometer separation) supported on thin films of amorphous zinc-tin-oxide have been characterized. After an initial filament-forming process, each device exhibited volatile, resistive switching. In the low resistance state, the transport mechanism and conductance depended on prior activity and on the imposed current limit, mimicking biologic synaptic plasticity. Microscopic observations performed on each device revealed nanoscale filaments between the electrodes. These filaments were subject to Rayleigh instability and exhibited relaxation times determined by their effective radii. The relaxation times and on:off resistance ratios suggest suitability for threshold switching selector devices.
A model of a High Voltage CMOS (HV-CMOS) Monolithic Active Pixel Sensor (MAPS) has been modelled using Technology Computer Aided Design (TCAD). The model has incorporated both the active region and the on-pixel readout circuits which were comprised of a source follower amplifier and an integrated charge amplifier. The simulation has examined the electrical characteristics and response output of a HV-CMOS MAPS sensor using typical dimensions, levels of doping in the structural layers and bias conditions for this sensor. The performance of two alternate designs of amplifier have been examined as a function of the operating parameters. The response of the sensor to the incidence of Minimum Ionizing Particles (MIPs) at different energies has been included in the model.
The electrical characteristics of Au/Ni/Ti/ n-SiC contacts have been examined as a function of implant dose (1013-1014 ions/cm2) at 5 KeV and temperature of annealing (750-1000 °C). Measurements of specific contact resistance, ρc, were approximately constant at lower implant doses until increasing at 1 x 1015 ions/cm2 for both C and P ions. Annealing at a temperature of 1000 °C has reduced the value of ρc by an order of magnitude to ∼1 x 10-6 Ω.cm2 at implant doses of 1013-1014 ions/cm2. Auger Electron Spectroscopy (AES) has shown that annealing at 1000 °C resulted in a strong indiffusion of the metallization layers at the interface.
Finite element modelling has been used to optimise the current/ voltage (I/V) characteristics of metal/ n-SiC and metal/ n-Si diodes incorporating a thin interfacial layer. The electrical properties of the diodes have been examined in relation to the polytype of SiC (3H, 4H or 6C), the doping level, NA, (1015 - 1018cm3) of the substrate, the defect state density, Dit and the work function of the Schottky metal, Φm. The modelling by Technology Computer-Aided Design (TCAD) has shown that the presence of an interfacial insulating layer with a thickness of 1.0 nm has reduced the reverse leakage current of the diode by a factor of ∼102 in Si and 1013 (from 10-19 A to 10-6 A) for SiC with only a minor reduction (∼ 0.8 times) in the forward current in SiC. The properties of the diodes have been modelled at room temperature without thermal annealing.
Carbon films deposited by filtered cathodic vacuum arc have been used to form high quality Schottky diodes on p-Si. Energetic deposition with an applied substrate bias of -1 kV and with a substrate temperature of 100 °C has produced carbon diodes with rectification ratios of ∼ 3 × 106, saturation currents of ∼0.02 nA and ideality factors close to unity (n = 1.05). Simulations were used to estimate the effective work function and the thickness of an interfacial mixed (C/SiO2) layer from the current/voltage characteristics of the diodes.
The effect of low energy implantation of P or C ions in 3C-SiC on the properties of Ti/Ni/Au contacts has been examined for doses in the range 1013-1015 ions/cm2. Measurements of specific contact resistance, ρc, were performed using the two-contact circular test structure. The magnitude of ρc for the Ti/Ni/Au contacts on unimplanted SiC was 1.29 x 10−6 Ω.cm2. The value of ρc increased significantly at an implant dose of 1 x 1015 ions/cm2. The dependence of ρc on ion dose has been measured using both C and P implant species.
Energetically-deposited carbon contacts to n-type 6H-SiC have exhibited either insulating, rectifying or ohmic electrical characteristics depending on the average energy of the depositing flux and the substrate temperature. Deposition at room temperature and at a low-medium average energy (<500 eV) has resulted in carbon with a low graphitic content and insulating electrical contacts. With higher average energy and at a moderately elevated temperature (∼100 °C), the higher graphitic content contacts were rectifying with an ideality factor, η, of ∼1.8 and barrier height of ∼0.88 eV. Oriented graphitic carbon deposited at 200 °C with biases exceeding 300 V formed ohmic contacts.
The formation of nickel germanide has been examined over a range of low temperatures (200-400 °C) in an attempt to minimize the thermal budget for the process. Cross-sectional Transmission Electron Microscopy (TEM) was used to determine the texture of the germanide layer and the morphology and constituent composition of the Ge/NiGe interface. The onset and completion of reaction between Ni and Ge were identified by means of a heated stage in combination with in-situ x-ray diffraction (XRD) measurements. The stages of reaction were also monitored using measurements of sheet resistance of the germanides by the Van der Pauw technique. The results have shown that the minimum temperature for the initiation of reaction of Ni and Ge to form NiGe was 225 °C. However, an annealing temperature > 275 °C was necessary for the extensive (and practical) formation of NiGe. Between 200 and 300 °C, the duration of annealing required for the formation of NiGe was significantly longer than at higher temperatures. The stoichiometry of the germanide was very close to NiGe (1:1) as determined using energy dispersive spectroscopy (EDS).
We describe the novel application of light coupling masks (LCM) in the lithographic patterning of fine structures in diamond films. A PDMS mask was used in the exposure of complex patterns of gratings in AZP 1205 resist on a substrate of Al/ diamond. The profiles of these grating patterns were then modified on a localized scale by a process of reflow of the resist. We report on the transfer of the patterns formed in resist by the LCMs into the diamond film using a sputtered Al layer as a mask. The two-stage process comprised etching of the pattern into the Al followed by transfer into the diamond film using CF4/ O2 and CHF3/ O2 gases. The presence of O2 in the CF4/ O2 and CHF3/ O2 gas mixtures produced Al oxides on the surface of the mask. The etch selectivity of the mask was greater in CF4/ O2 than in CHF3/ O2 gases and was only weakly dependent on the concentration of O2 (0-12 sccm).
The reactive ion etching of diamond in O2, CF4/O2, CHF3/O2, O2/Ar) discharges has been examined as a function of bias voltage, flow rate and composition of the gas mixtures. Etching in O2 and O2/Ar plasmas (with flow ratio of O2/Ar >25% ) was characterised by a high etch rate (∼35 nm/min) and an increase in surface roughness with rising bias voltage. The CF4/O2 plasmas also produced a high etch rate (∼50 nm/min) but with only minor dependence of roughness on bias voltage. In comparison, the O2/Ar (with O2/Ar flow ratio <25%) and CHF3/O2 plasmas resulted in a low etch rate (7-10 nm/min). The high and low rate regimes were identified as ion- enhanced chemical etching and physical sputtering respectively. Etching in the O2/Ar plasmas has been attributed to a combination of the two processes dependent on the O2 content.
Diamond films were implanted with Au or O ions at multiple energies in order to produce a uniform region of C vacancies. Analysis of the implanted films by Raman spectroscopy has shown that the proportion of non-diamond or amorphous carbon increased with dose (5 × 1013 − 5 × 1015 ions/cm2). For implantation with Au ions, a complete amorphisation near to the surface was evident at a dose of 5 × 1015 ions/cm2. We have examined the ion beam etch (IBE) rate of the films as a function of the implant species and dose. The etching experiments were performed using either Ar or Ar/O2 gases at a bias energy of 500 -1,000 eV. In Ar gas, the process of sputter etching has produced a similar increase in etch rate with dose for both the Au and O implants. In Ar/ O2 gases, the process of ion-enhanced chemical etching produced greater etch rates than obtained in Ar gas with higher rates for the Au than the O implants.
The patterning of strontium-doped lead zirconium titanate (PSZT) and lanthanum-doped lead zirconium titanate (PLZT) films has been examined using excimer laser radiation. Both types of film were deposited by rf magnetron sputtering using in-situ heating and a controlled cooling rate in order to obtain the perovskite-oriented phase. The depth of laser ablation in both PSZT and PLZT films showed a logarithmic dependence on fluence. The threshold fluence required to initiate ablation was ∼1.25 mJ/cm2 for PLZT and ∼1.87 mJ/cm2 for PSZT films. The ablation rate of PLZT films was slightly higher than that of PSZT films over the range of fluence (10-150 J/cm2) and increased linearly with number of pulses. The higher ablation rate of PLZT films has been attributed to the finer grainsize (160-200 nm) than in the PSZT films (1.0-1.2 µm).
The ablation of strontium-doped lead zirconate titanate (PSZT) and lanthanum-doped lead zirconate titanate (PLZT) films has been examined using a 5 ns pulsed excimer laser. Individual squares were patterned with sides in the range of 10-30 µm using single and multiple pulses. The depth of ablation in PLZT films was higher at all fluences than in PSZT films. The morphology of the etched surfaces has comprised the formation of globules which had diameters of 200-250 nm in PLZT and 1400-1600 nm in PSZT films. The diameter of the globules has been shown to increase with fluence until reaching an approximately constant size at >20 J/cm2 in both types of film. The composition of the films following ablation has been analyzed using x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray (EDX) spectroscopy.
A novel method for forming interdigitated electrodes for GHz Surface acoustic wave (SAW) devices on diamond using a damascene-like polishing technique is described. Low aspect ratio Al electrodes are recessed into the diamond substrates to create a near planar surface. This allows the deposition of higher quality oriented ZnO. CVD diamond samples were ion-beam etched with groove widths in the range 1-5μm to a depth of 80-120nm. Al (120nm thick) was sputter deposited on to the etched diamond and was polished using either (i) a solution of 0.05μm silica on a neoprene polishing cloth or (ii) using a ∼0.12mm thick PVDF (polyvinylidene difluoride) filter pad with colloidal solutions of silica. Using AFM scans and optical microscopy it was observed that the combination of method (i) with the small sample size resulted in significant hollowing-out of the Al electrodes and complete removal of Al from over 90% of the pad-interconnect area. The alternative technique in (ii) demonstrated far less Al removal and better uniformity in the electrode patterns.
Many studies of Barium Strontium Titanate (BST) thin films for RF / microwave applications have employed MgO, LaAlO3 or Pt/Si as the substrate material for BST deposition. However, there have been relatively few reports of BST films grown on sapphire, despite the excellent microwave properties of this material. In this investigation, BST thin films were deposited by RF magnetron sputtering on (001) single crystal c-plane sapphire substrates. Interdigitated capacitors (IDCs) patterned on the film surface were used to measure the dielectric tunability and loss tangent at microwave frequencies. Thick Au conductors were electroplated to minimize conductor losses. Post deposition annealing in air was found to significantly improve the tunability of the sputtered films.
Despite the prevalence and clinical significance of borderline personality disorder, its treatment remains understudied.
To evaluate treatment with variably dosed olanzapine in individuals with borderline personality disorder.
In this 12-week randomised, double-blind trial, individuals received olanzapine (2.5–20 mg/day; n=155) or placebo (n=159) (trial registry: NCT00091650). The primary efficacy measure was baseline to end-point change on the Zanarini Rating Scale for Borderline Personality Disorder (ZAN–BPD) using last-observation-carried-forward methodology.
Both olanzapine and placebo groups showed significant improvements but did not differ in magnitude at end-point (76.56 v. 76.25, P=0.661). Response rates (50% reduction in ZAN–BPD) were 64.7% with olanzapine and 53.5% with placebo (P=0.062); however, time to response was significantly shorter for olanzapine (P=0.022). Weight gain was significantly greater (2.86 v. 70.35 kg, P50.001), with higher incidence of treatment-emergent abnormal high levels of prolactin for the olanzapine group.
Individuals treated with olanzapine and placebo showed significant but not statistically different improvements on overall symptoms of borderline personality disorder. The types of adverse events observed with olanzapine treatment appeared similar to those observed previously in adult populations.