Three-Dimensional Integration of InAs Nanowires by Template-Assisted Selective Epitaxy on Tungsten.

3D integration of III-V semiconductors with Si CMOS is highly attractive since it allows combining new functions such as photonic and analog devices with digital signal processing circuitry. Thus far, most 3D integration approaches have used epitaxial growth on Si, layer transfer by wafer bonding, or die-to-die packaging. Here we present low-temperature integration of InAs on W using Si3N4 template assisted selective area metal-organic vapor-phase epitaxy (MOVPE). Despite growth nucleation on polycrystalline W, we can obtain a high yield of single-crystalline InAs nanowires, as observed by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The nanowires exhibit a mobility of 690 cm2/(V s), a low-resistive, Ohmic electrical contact to the W film, and a resistivity which increases with diameter attributed to increased grain boundary scattering. These results demonstrate the feasibility for single-crystalline III-V back-end-of-line integration with a low thermal budget compatible with Si CMOS.

Low-Temperature Characteristics of Nanowire Network Demultiplexer for Qubit Biasing.

In current quantum computers, most qubit control electronics are connected to the qubit chip inside the cryostat by cables at room temperature. This poses a challenge when scaling the quantum chip to an increasing number of qubits. We present a lateral nanowire network 1-to-4 demultiplexer design fabricated by selective area grown InGaAs on InP, suitable for on chip routing of DC current for qubit biasing. We have characterized the device at cryogenic temperatures, and at 40 mK the device exhibits a minimum inverse subthreshold slope of 2 mV/dec, which is encouraging for low power operation. At low drain bias, the transmission breaks up into several resonance peaks due to a rough conduction band edge; this is qualitatively explained by a simple model based on a 1D real space tight-binding nonequilibrium Green's functions model.

Oxygen relocation during HfO2 ALD on InAs.

Atomic layer deposition (ALD) is one of the backbones for today's electronic device fabrication. A critical property of ALD is the layer-by-layer growth, which gives rise to the atomic-scale accuracy. However, the growth rate - or growth per cycle - can differ significantly depending on the type of system, molecules used, and several other experimental parameters. Typically, ALD growth rates are constant in subsequent ALD cycles, making ALD an outstanding deposition technique. However, contrary to this steady-state - when the ALD process can be entirely decoupled from the substrate on which the material is grown - the deposition's early stage does not appear to follow the same kinetics, chemistry, and growth rate. Instead, it is to a large extent determined by the surface composition of the substrate. Here, we present evidence of oxygen relocation from the substrate-based oxide, either the thermal or native oxide of InAs, to the overlayer of HfO2 in the initial ALD phase. This phenomenon enables control of the thickness of the initial ALD layer by controlling the surface conditions of the substrate prior to ALD. On the other hand, we observe a complete removal of the native oxide from InAs already during the first ALD half-cycle, even if the thickness of the oxide layer exceeds one monolayer, together with a self-limiting thickness of the ALD layer of a maximum of one monolayer of HfO2. These observations not only highlight several limitations of the widely used ligand exchange model, but they also give promise for a better control of the industrially important self-cleaning effect of III-V semiconductors, which is crucial for future generation high-speed MOS.

Is What You See What You Get? Perceptions of Personal Trainers' Competence, Knowledge, and Preferred Sex of Personal Trainer Relative to Physique.

ABSTRACT: Boerner, PR, Polasek, KM, True, L, Lind, E, and Hendrick, JL. Is what you see what you get? Perceptions of personal trainers' competence, knowledge, and preferred sex of personal trainer relative to physique. J Strength Cond Res 35(7): 1949-1955, 2021-The role that a personal trainer's (PT) physique plays in how potential clients perceive the PT is an understudied, yet potentially powerful, area of inquiry that has important professional implications. The purpose of this study was to investigate how a PT's physique could influence perceptions of his/her (a) PT competence, (b) level of personal training knowledge, and (c) preferred sex of the PT. Subjects (n = 191) were presented with pictures of male and female volunteers labeled as PTs. The pictures emphasized physique and consisted of varying body types (ectomorph, mesomorph, and endomorph) and muscularity (muscular vs. nonmuscular). Subjects examined pictures to answer surveys to rate trainers' competence, knowledge, and preferred sex of PT. Personal trainer physique significantly influenced individuals' perceptions of trainer characteristics. Both mesomorphic and ectomorphic body types were rated as more competent than an endomorphic body type. Muscular PTs were perceived to be significantly more knowledgeable and competent than their nonmuscular peers. Female PTs were perceived as more competent and knowledgeable than male PTs. Findings also suggested many more males preferred to work with a male PT while females lacked consensus. Collectively, PT physique seems to have a profound influence whether they are approached or avoided. These findings may have implications for how PTs market themselves to potential clients.

Impact of source doping on the performance of vertical InAs/InGaAsSb/GaSb nanowire tunneling field-effect transistors.

In this paper, we analyze experimental data from state-of-the-art vertical InAs/InGaAsSb/GaSb nanowire tunneling field-effect transistors (TFETs) to study the influence of source doping on their performance. Overall, the doping level impacts both the off-state and on-state performance of these devices. Separation of the doping from the heterostructure improved the subthreshold swing of the devices. The best devices reached a point subthreshold swing of 30 mV/dec at 100 x higher currents than previous Si-based TFETs. However, separation of doping from the heterostructure had a significant impact on the on-state performance of these devices due to effects related to source depletion. An increase in the doping level helped to improve the on-state performance, which also increased the subthreshold swing. Thus, further optimization of doping incorporation with the heterostructure will help to improve vertical InAs/InGaAsSb/GaSb nanowire TFETs.

Vertical InAs/InGaAs Heterostructure Metal-Oxide-Semiconductor Field-Effect Transistors on Si.

III-V compound semiconductors offer a path to continue Moore's law due to their excellent electron transport properties. One major challenge, integrating III-V's on Si, can be addressed by using vapor-liquid-solid grown vertical nanowires. InAs is an attractive material due to its superior mobility, although InAs metal-oxide-semiconductor field-effect transistors (MOSFETs) typically suffer from band-to-band tunneling caused by its narrow band gap, which increases the off-current and therefore the power consumption. In this work, we present vertical heterostructure InAs/InGaAs nanowire MOSFETs with low off-currents provided by the wider band gap material on the drain side suppressing band-to-band tunneling. We demonstrate vertical III-V MOSFETs achieving off-current below 1 nA/µm while still maintaining on-performance comparable to InAs MOSFETs; therefore, this approach opens a path to address not only high-performance applications but also Internet-of-Things applications that require low off-state current levels.

Individual Defects in InAs/InGaAsSb/GaSb Nanowire Tunnel Field-Effect Transistors Operating below 60 mV/decade.

Tunneling field-effect transistors (TunnelFET), a leading steep-slope transistor candidate, is still plagued by defect response, and there is a large discrepancy between measured and simulated device performance. In this work, highly scaled InAs/InxGa1-xAsySb1-y/GaSb vertical nanowire TunnelFET with ability to operate well below 60 mV/decade at technically relevant currents are fabricated and characterized. The structure, composition, and strain is characterized using transmission electron microscopy with emphasis on the heterojunction. Using Technology Computer Aided Design (TCAD) simulations and Random Telegraph Signal (RTS) noise measurements, effects of different type of defects are studied. The study reveals that the bulk defects have the largest impact on the performance of these devices, although for these highly scaled devices interaction with even few oxide defects can have large impact on the performance. Understanding the contribution by individual defects, as outlined in this letter, is essential to verify the fundamental physics of device operation, and thus imperative for taking the III-V TunnelFETs to the next level.

Low Trap Density in InAs/High-k Nanowire Gate Stacks with Optimized Growth and Doping Conditions.

In this paper, we correlate the growth of InAs nanowires with the detailed interface trap density (Dit) profile of the vertical wrap-gated InAs/high-k nanowire semiconductor-dielectric gate stack. We also perform the first detailed characterization and optimization of the influence of the in situ doping supplied during the nanowire epitaxial growth on the sequential transistor gate stack quality. Results show that the intrinsic nanowire channels have a significant reduction in Dit as compared to planar references. It is also found that introducing tetraethyltin (TESn) doping during nanowire growth severely degrades the Dit profile. By adopting a high temperature, low V/III ratio tailored growth scheme, the influence of doping is minimized. Finally, characterization using a unique frequency behavior of the nanowire capacitance-voltage (C-V) characteristics reveals a change of the dopant incorporation mechanism as the growth condition is changed.

InAs nanowire MOSFETs in three-transistor configurations: single balanced RF down-conversion mixers.

Integration of III-V semiconductors on Si substrates allows for the realization of high-performance, low power III-V electronics on the Si-platform. In this work, we demonstrate the implementation of single balanced down-conversion mixer circuits, fabricated using vertically aligned InAs nanowire devices on Si. A thin, highly doped InAs buffer layer has been introduced to reduce the access resistance and serve as a bottom electrode. Low-frequency voltage conversion gain is measured up to 7 dB for a supply voltage of 1.5V. Operation of these mixers extends into the GHz regime with a -3 dB cut-off frequency of 2 GHz, limited by the optical lithography system used. The circuit dc power consumption is measured at 3.9 mW.

Combining axial and radial nanowire heterostructures: radial Esaki diodes and tunnel field-effect transistors.

The ever-growing demand on high-performance electronics has generated transistors with very impressive figures of merit (Radosavljevic et al., IEEE Int. Devices Meeting 2009, 1-4 and Cho et al., IEEE Int. Devices Meeting 2011, 15.1.1-15.1.4). The continued scaling of the supply voltage of field-effect transistors, such as tunnel field-effect transistors (TFETs), requires the implementation of advanced transistor architectures including FinFETs and nanowire devices. Moreover, integration of novel materials with high electron mobilities, such as III-V semiconductors and graphene, are also being considered to further enhance the device properties (del Alamo, Nature 2011, 479, 317-323, and Liao et al., Nature 2010, 467, 305-308). In nanowire devices, boosting the drive current at a fixed supply voltage or maintaining a constant drive current at a reduced supply voltage may be achieved by increasing the cross-sectional area of a device, however at the cost of deteriorated electrostatics. A gate-all-around nanowire device architecture is the most favorable electrostatic configuration to suppress short channel effects; however, the arrangement of arrays of parallel vertical nanowires to address the drive current predicament will require additional chip area. The use of a core-shell nanowire with a radial heterojunction in a transistor architecture provides an attractive means to address the drive current issue without compromising neither chip area nor device electrostatics. In addition to design advantages of a radial transistor architecture, we in this work illustrate the benefit in terms of drive current per unit chip area and compare the experimental data for axial GaSb/InAs Esaki diodes and TFETs to their radial counterparts and normalize the electrical data to the largest cross-sectional area of the nanowire, i.e. the occupied chip area, assuming a vertical device geometry. Our data on lateral devices show that radial Esaki diodes deliver almost 7 times higher peak current, Jpeak = 2310 kA/cm(2), than the maximum peak current of axial GaSb/InAs(Sb) Esaki diodes per unit chip area. The radial TFETs also deliver high peak current densities Jpeak = 1210 kA/cm(2), while their axial counterparts at most carry Jpeak = 77 kA/cm(2), normalized to the largest cross-sectional area of the nanowire.

Uniform and position-controlled InAs nanowires on 2" Si substrates for transistor applications.

This study presents a novel approach for indirect integration of InAs nanowires on 2'' Si substrates. We have investigated and developed epitaxial growth of InAs nanowires on 2'' Si substrates via the introduction of a thin yet high-quality InAs epitaxial layer grown by metalorganic vapor phase epitaxy. We demonstrate well-aligned nanowire growth including precise position and diameter control across the full wafer using very thin epitaxial layers (<300 nm). Statistical analysis results performed on the grown nanowires across the 2'' wafer size verifies our full control on the grown nanowire with 100% growth yield. From the crystallographic viewpoint, these InAs nanowires are predominantly of wurtzite structure. Furthermore, we show one possible device application of the aforementioned structure in vertical wrap-gated field-effect transistor geometry. The vertically aligned InAs nanowires are utilized as transistor channels and the InAs epitaxial layer is employed as the source contact. A high uniformity of the device characteristics for numerous transistors is further presented and RF characterization of these devices demonstrates an f(t) of 9.8 GHz.

Doping Profiles in Ultrathin Vertical VLS-Grown InAs Nanowire MOSFETs with High Performance.

Thin vertical nanowires based on III-V compound semiconductors are viable candidates as channel material in metal oxide semiconductor field effect transistors (MOSFETs) due to attractive carrier transport properties. However, for improved performance in terms of current density as well as contact resistance, adequate characterization techniques for resolving doping distribution within thin vertical nanowires are required. We present a novel method of axially probing the doping profile by systematically changing the gate position, at a constant gate length L g of 50 nm and a channel diameter of 12 nm, along a vertical nanowire MOSFET and utilizing the variations in threshold voltage V T shift (∼100 mV). The method is further validated using the well-established technique of electron holography to verify the presence of the doping profile. Combined, device and material characterizations allow us to in-depth study the origin of the threshold voltage variability typically present for metal organic chemical vapor deposition (MOCVD)-grown III-V nanowire devices.

Relationships among Actual Motor Competence, Perceived Motor Competence, and Health-Related Fitness in College-Aged Males.

Actual motor competence (MC), perceived motor competence (PMC), and health-related fitness (HRF) exhibit a dynamic and reciprocal relationship in child populations, but little is known about the nature of these relationships in young adulthood. The purpose of the study was to assess these relationships in a sample of college-aged males. A total of 55 participants enrolled in an undergraduate Kinesiology course completed the study. Perceived motor competence (PMC) was assessed with the Physical Self-Perception Profile questionnaire; MC was assessed using maximum throw and kick speed and maximum jump distance; HRF was assessed with a two-minute push-up test, two-minute sit-up test, and the Multistage 20-m Shuttle Run Test. Pearson's bivariate correlations were calculated to assess relationships among PMC total score, MC scores, and HRF scores. Two separate indices were calculated to create composite total MC and total HRF scores used for subsequent analyses. Significant correlations were found between PMC total score, MC index, and HRF index. Multiple linear regressions were used for analyzing predictive measures for HRF and PMC scores. From the two regression models, significance varied among total MC scores, PMC scores, and HRF individual measures. These findings may suggest that relationships among MC, HRF, and PMC strengthen over developmental time in young adult males.

Do 'mind over muscle' strategies work? Examining the effects of attentional association and dissociation on exertional, affective and physiological responses to exercise.

Despite the well established physical and psychological benefits derived from leading a physically active life, rates of sedentary behaviour remain high. Dropout and non-compliance are major contributors to the problem of physical inactivity. Perceptions of exertion, affective responses (e.g. displeasure or discomfort), and physiological stress could make the exercise experience aversive, particularly for beginners. Shifting one's attentional focus towards environmental stimuli (dissociation) instead of one's body (association) has been theorized to enhance psychological responses and attenuate physiological stress. Research evidence on the effectiveness of attentional focus strategies, however, has been perplexing, covering the entire gamut of possible outcomes (association and dissociation having been shown to be both effective and ineffective). This article examines the effects of manipulations of attentional focus on exertional and affective responses, as well as on exercise economy and tolerance. The possible roles of the characteristics of the exercise stimulus (intensity, duration) and the exercise participants, methodological issues, and limitations of experimental designs are discussed. In particular, the critical role of exercise intensity is emphasized. Dissociative strategies may be more effective in reducing perceptions of exertion and enhancing affective responses at low to moderate exercise intensities, but their effectiveness may be diminished at higher and near-maximal levels, at which physiological cues dominate. Conversely, associative strategies could enable the exerciser to regulate intensity to avoid injury or overexertion. Thus, depending on intensity, both strategies have a place in the 'toolbox' of the public health or exercise practitioner as methods of enhancing the exercise experience and promoting long-term compliance.

The affective impact of exercise intensity that slightly exceeds the preferred level: 'pain' for no additional 'gain'.

We examined the affective consequences of an exercise intensity that slightly exceeded the preferred level. Twenty-five middle-age sedentary women participated in two 20-min treadmill exercise bouts, one during which they could select the speed and one during which the speed was 10 per cent higher than the self-selected. During the bout at self-selected intensity, ratings of pleasure remained stable, whereas during the imposed-intensity bout pleasure decreased. Therefore, even a minor increase in exercise intensity beyond the level that a new exerciser would have self-selected can bring about a decrease in pleasure. Over time, such experiences could lower adherence.

Can self-reported tolerance of exercise intensity play a role in exercise testing?

INTRODUCTION/PURPOSE: To examine the relationship between self-reported tolerance of exercise intensity, measured by the Preference for and Tolerance of Exercise Intensity Questionnaire, and the amount of time individuals persevered during incremental treadmill tests to volitional fatigue beyond the point at which they had reached their ventilatory threshold. METHODS: The participants in study 1 were college age and physically active (14 women, 16 men). The participants in study 2 were 24 middle-aged women who were healthy but sedentary. RESULTS: Tolerance was related to the duration after the ventilatory threshold, and this relationship remained after age, body mass index, and self-reported frequency and duration of habitual physical activity (study 1) or after age, body mass index, and maximal aerobic capacity (study 2) had been taken into account. CONCLUSION: Self-reports of exercise intensity tolerance might account for variability in the extent to which individuals persevere during exercise tests. Identifying individuals predisposed to under- or overexertion could be of value in exercise testing and prescription.

Run Economy on a Normal and Lower Body Positive Pressure Treadmill.

Lower body positive pressure (LBPP) treadmill running is used more frequently in clinical and athletic settings. Accurate caloric expenditure is required for proper exercise prescription, especially for obese patients performing LBPP exercise. It is unclear if running on LBPP changes running economy (RE) in proportion to the changes in body weight. The purpose of the study was to measure the oxygen consumption (VO2) and running economy (RE) of treadmill running at normal body weight and on LBPP. Twenty-three active, non-obese participants (25.8±7.2 years; BMI = 25.52±3.29 kg·m-2) completed two bouts of running exercise in a counterbalanced manner: (a) on a normal treadmill (NT) and (b) on a LBPP treadmill at 60% (40% of body weight supported) for 4 min at 2.24 (5 mph), 2.68 (6 mph), and 3.13 m·s-1 (7 mph). Repeated measures ANOVA showed a statistically significant interaction in RE among trials, F(2, 44) = 6.510, p <.0005, partial η2 = 0.228. An examination of pairwise comparisons indicated that RE was significantly greater for LBPP across the three speeds (p < 0.005). As expected, LBPP treadmill running resulted in significantly lower oxygen consumption at all three running speeds. We conclude that RE (ml O2·kg-1·km-1) of LBPP running is significantly poorer than normal treadmill running, and the ~30% change in absolute energy cost is not as great as predicted by the change in body weight (40%).

Four Weeks of Off-Season Training Improves Peak Oxygen Consumption in Female Field Hockey Players.

The purpose of the study was to examine the changes in peak oxygen consumption ( V ˙O2peak) and running economy (RE) following four-weeks of high intensity training and concurrent strength and conditioning during the off-season in collegiate female field hockey players. Fourteen female student-athletes (age 19.29 ± 0.91 years) were divided into two training groups, matched from baseline V ˙O2peak: High Intensity Training (HITrun; n = 8) and High Intensity Interval Training (HIIT; n = 6). Participants completed 12 training sessions. HITrun consisted of 30 min of high-intensity running, while HIIT consisted of a series of whole-body high intensity Tabata-style intervals (75⁻85% of age predicted maximum heart rate) for a total of four minutes. In addition to the interval training, the off-season training included six resistance training sessions, three team practices, and concluded with a team scrimmage. V ˙O2peak was measured pre- and post-training to determine the effectiveness of the training program. A two-way mixed (group × time) ANOVA showed a main effect of time with a statistically significant difference in V ˙O2peak from pre- to post-testing, F(1, 12) = 12.657, p = 0.004, partial η² = 0.041. Average (±SD) V ˙O2peak increased from 44.64 ± 3.74 to 47.35 ± 3.16 mL·kg-1·min-1 for HIIT group and increased from 45.39 ± 2.80 to 48.22 ± 2.42 mL·kg-1·min-1 for HITrun group. Given the similar improvement in aerobic power, coaches and training staff may find the time saving element of HIIT-type conditioning programs attractive.

Quantized Conduction and High Mobility in Selectively Grown In(x)Ga(1-x)As Nanowires.

We report measured quantized conductance and quasi-ballistic transport in selectively regrown In0.85Ga0.15As nanowires. Very low parasitic resistances obtained by regrowth techniques allow us to probe the near-intrinsic electrical properties, and we observe several quantized conductance steps at 10 K. We extract a mean free path of 180 ± 40 nm and an effective electron mobility of 3300 ± 300 cm(2)/V·s, both at room temperature, which are among the largest reported values for nanowires of similar dimensions. In addition, optical characterization of the nanowires by photoluminescence and Raman measurement is performed. We find an unintentional increase of indium in the InxGa1-xAs composition relative to the regrown film layer, as well as partial strain relaxation.

Affective responses to increasing levels of exercise intensity in normal-weight, overweight, and obese middle-aged women.

At least 60 min of daily physical activity (PA) are recommended for weight control, a target achieved by only 3% of obese (OB) women. The purposes of this study were to examine (i) the affective responses of normal-weight (NW), overweight (OW), and OB middle-aged sedentary women to exercise of increasing intensity and (ii) the relationship of affective responses to self-efficacy and social physique anxiety. The women participated in a graded treadmill protocol to volitional exhaustion while providing ratings of pleasure-displeasure and perceived activation each minute. The Activation Deactivation Adjective Check List (AD ACL) was also completed before and after exercise. The affective responses of NW and OW women did not differ. However OB women gave lower pleasure ratings during the incremental protocol and reported lower Energy scores immediately after the protocol. Social physique anxiety, but not self-efficacy, was inversely related to pleasure and energy. The lower levels of pleasure and energy experienced by OB than nonobese women could account in part for their dramatically low levels of PA participation. Modifying the cognitive antecedents of social physique anxiety might be a useful intervention strategy.