33 research outputs found
Near-thermal limit gating in heavily-doped III-V semiconductor nanowires using polymer electrolytes
Doping is a common route to reducing nanowire transistor on-resistance but
has limits. High doping level gives significant loss in gate performance and
ultimately complete gate failure. We show that electrolyte gating remains
effective even when the Be doping in our GaAs nanowires is so high that
traditional metal-oxide gates fail. In this regime we obtain a combination of
sub-threshold swing and contact resistance that surpasses the best existing
p-type nanowire MOSFETs. Our sub-threshold swing of 75 mV/dec is within 25% of
the room-temperature thermal limit and comparable with n-InP and n-GaAs
nanowire MOSFETs. Our results open a new path to extending the performance and
application of nanowire transistors, and motivate further work on improved
solid electrolytes for nanoscale device applications.Comment: 6 pages, 2 figures, supplementary available at journa
Using ultra-thin parylene films as an organic gate insulator in nanowire field-effect transistors
We report the development of nanowire field-effect transistors featuring an
ultra-thin parylene film as a polymer gate insulator. The room temperature,
gas-phase deposition of parylene is an attractive alternative to oxide
insulators prepared at high temperatures using atomic layer deposition. We
discuss our custom-built parylene deposition system, which is designed for
reliable and controlled deposition of <100 nm thick parylene films on III-V
nanowires standing vertically on a growth substrate or horizontally on a device
substrate. The former case gives conformally-coated nanowires, which we used to
produce functional -gate and gate-all-around structures. These give
sub-threshold swings as low as 140 mV/dec and on/off ratios exceeding at
room temperature. For the gate-all-around structure, we developed a novel
fabrication strategy that overcomes some of the limitations with previous
lateral wrap-gate nanowire transistors. Finally, we show that parylene can be
deposited over chemically-treated nanowire surfaces; a feature generally not
possible with oxides produced by atomic layer deposition due to the surface
`self-cleaning' effect. Our results highlight the potential for parylene as an
alternative ultra-thin insulator in nanoscale electronic devices more broadly,
with potential applications extending into nanobioelectronics due to parylene's
well-established biocompatible properties
InAs nanowire transistors with multiple, independent wrap-gate segments
We report a method for making horizontal wrap-gate nanowire transistors with
up to four independently controllable wrap-gated segments. While the step up to
two independent wrap-gates requires a major change in fabrication methodology,
a key advantage to this new approach, and the horizontal orientation more
generally, is that achieving more than two wrap-gate segments then requires no
extra fabrication steps. This is in contrast to the vertical orientation, where
a significant subset of the fabrication steps needs to be repeated for each
additional gate. We show that cross-talk between adjacent wrap-gate segments is
negligible despite separations less than 200 nm. We also demonstrate the
ability to make multiple wrap-gate transistors on a single nanowire using the
exact same process. The excellent scalability potential of horizontal wrap-gate
nanowire transistors makes them highly favourable for the development of
advanced nanowire devices and possible integration with vertical wrap-gate
nanowire transistors in 3D nanowire network architectures.Comment: 18 pages, 5 figures, In press for Nano Letters (DOI below
Overvaluation of shape and weight in adolescents with anorexia nervosa: does shape concern or weight concern matter more for treatment outcome?
BACKGROUND: Overvaluation of shape and weight is a key diagnostic feature of anorexia nervosa (AN); however, limited research has evaluated the clinical utility of differentiating between weight versus shape concerns. Understanding differences in these constructs may have important implications for AN treatment given the focus on weight regain. This study examined differences in treatment outcome between individuals whose primary concern was weight versus those whose primary concern was shape in a randomized controlled trial of treatment for adolescent AN. METHODS: Data were drawn from a two-site randomized controlled trial that compared family-based treatment and adolescent focused therapy for AN. Chi-square tests and logistic regression analyses were conducted. RESULTS: Thirty percent of participants presented with primary weight concern (n = 36; defined as endorsing higher Eating Disorder Examination (EDE) Weight Concern than Shape Concern subscale scores); 60 % presented with primary shape concern (n = 72; defined as endorsing higher EDE Shape Concern than Weight Concern scores). There were no significant differences between the two groups in remission status at the end of treatment. Treatment did not moderate the effect of group status on achieving remission. CONCLUSIONS: Results suggest that treatment outcomes are comparable between adolescents who enter treatment for AN with greater weight concerns and those who enter treatment with greater shape concerns. Therefore, treatment need not be adjusted based on primary weight or primary shape concerns
Achieving short high-quality gate-all-around structures for horizontal nanowire field-effect transistors
We introduce a fabrication method for gate-all-around nanowire field-effect transistors. Single nanowires were aligned perpendicular to underlying bottom gates using a resist-trench alignment technique. Top gates were then defined aligned to the bottom gates to form gate-all-around structures. This approach overcomes significant limitations in minimal obtainable gate length and gate-length control in previous horizontal wrap-gated nanowire transistors that arise because the gate is defined by wet-etching. In the method presented here gate-length control is limited by the resolution of the electron-beam-lithography process. We demonstrate the versatility of our approach by fabricating a device with an independent bottom gate, top gate, and gate-all-around structure as well as a device with three independent gate-all-around structures with 300, 200, and 150 nm gate length. Our method enables us to achieve subthreshold swings as low as 38 mV dec-1 at 77 K for a 150 nm gate length