Imaging a 1-electron InAs quantum dot in an InAs/InP nanowire

Nanowire heterostructures define high-quality few-electron quantum dots for nanoelectronics, spintronics and quantum information processing. We use a cooled scanning probe microscope (SPM) to image and control an InAs quantum dot in an InAs/InP nanowire, using the tip as a movable gate. Images of dot conductance vs. tip position at T = 4.2 K show concentric rings as electrons are added, starting with the first electron. The SPM can locate a dot along a nanowire and individually tune its charge, abilities that will be very useful for the control of coupled nanowire dots

The electrical and structural properties of n-type InAs nanowires grown from metal-organic precursors

The electrical and structural properties of 〈111〉B-oriented InAs nanowires grown using metal-organic precursors have been studied. On the basis of electrical measurements it was found that the trends in carbon incorporation are similar to those obser

Empowering aspects for healthy food and physical activity habits : adolescents’ experiences of a school-based intervention in a disadvantaged urban community

Purpose: This study aimed to describe adolescents’ experiences of participating in a health-promoting school-based intervention regarding food and physical activity, with a focus on empowering aspects.  Method: The school was located in a urban disadvantaged community in Sweden, characterized by poorer self-reported health and lower life expectancy than the municipality average. Focus group interviews with adolescents (29 girls, 20 boys, 14–15 years) and their teachers (n = 4) were conducted two years after intervention. Data were categorized using qualitative content analysis.  Results:  A theme was generated, intersecting with all the categories: Gaining control over one’s health: deciding, trying, and practicing together, in new ways, using reflective tools. The adolescents appreciated influencing the components of the intervention and collaborating with peers in active learning activities such as practicing sports and preparing meals. They also reported acquiring new health information, that trying new activities was inspiring, and the use of pedometers and photo-food diaries helped them reflect on their health behaviours. The adolescents’ experiences were also echoed by their teachers.  Conclusions:  To facilitate empowerment and stimulate learning, health-promotion interventions targeting adolescents could enable active learning activities in groups, by using visualizing tools to facilitate self-reflection, and allowing adolescents to influence intervention activities.Funding: Department of Food and Nutrition and Sport Science at the University of Gothenburg & Swedish Nutrition FoundationHow-to-Act

Deposition of HfO2 on InAs by atomic-layer deposition

Metal-oxide-semiconductor (MOS) capacitors are formed on bulk InAs substrates by atomic-layer deposition (ALD) of HfO2. Prior to film growth, InAs substrates receive a wet-chemical treatment of HCl, buffered HF (BHF), or (NH4)(2)S. Hafnium dioxide films are grown using 75 ALD cycles with substrate temperatures of 100, 200, and 300 degrees C. Substrate temperature is found to have a significant influence on the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the capacitors, while the influence of substrate pretreatment manifests itself in interface trap density, D-it, as measured by the Terman method. (C) 2009 Elsevier B.V. All rights reserved

Development of a vertical wrap-gated InAs FET

In this paper, we report on the development of a vertical wrap-gated field-effect transistor based on epitaxially grown InAs nanowires. We discuss some of the important steps involved in the growth and processing, such as nanowire position control, in si

Thermal conductivity of indium arsenide nanowires with wurtzite and zinc blende phases

The thermal conductivity of wurtzite and zinc blende indium arsenide nanowires was measured using a microfabricated device, with the crystal structure of each sample controlled during growth and determined by transmission electron microscopy. Nanowires of both phases showed a reduction of the thermal conductivity by a factor of 2 or more compared to values reported for zinc blende indium arsenide bulk crystals within the measured temperature range. Theoretical models were developed to analyze the measurement results and determine the effect of phase on phonon transport. Branch-specific phonon dispersion data within the discretized first Brillouin zone were calculated from first principles and used in numerical models of volumetric heat capacity and thermal conductivity. The combined results of the experimental and theoretical studies suggest that wurtzite indium arsenide possesses similar volumetric heat capacity, weighted average group velocity, weighted average phonon-phonon scattering mean free path, and anharmonic scattering-limited thermal conductivity as the zinc blende phase. Hence, we attribute the differing thermal conductivity values observed in the indium arsenide nanowires of different phases to differences in the surface scattering mean free paths between the nanowire samples