Investigation of the electrical properties of Si₁-×Ge× channel pMOSFETs with high-κ dielectrics

It is now apparent that the continued performance enhancements of silicon metal-oxide-semiconductor field effect transistors (MOSFETs) can no longer be met by scaling alone. High-mobility channel materials such as strained Si1-xGex and Ge are now being seriously considered to maintain the performance requirements specified by the semiconductor industry. In addition, alternative gate dielectric, or high-κ dielectrics, will also be required to meet gate leakage requirements. This work investigates the properties of using strained Si1-xGex or Ge as alternative channel materials for pMOSFETs incorporating hafnium oxide (HfO2) high-κ gate dielectric. Whilst the SiGe pMOSFETs (x = 0.25) exhibited an enhancement in hole mobility (300 K) over comparable silicon control pMOSFETs with sputtered HfO2 dielectric, high Coulomb scattering and surface roughness scattering relating to the dielectric deposition process meant that the effective hole mobilities were degraded with respect to the silicon universal curve. Germanium channel pMOSFETs with halo-doping and HfO2 gate dielectric deposited by atomic layer deposition showed high hole mobilities of 230 cm2V-1s-1 and 480 cm2V-1s-1 at room temperature and 77 K, respectively. Analysis of the off-state current for the Ge pMOSFETs over a range of temperatures indicated that band-to-band tunnelling, gate-induced drain leakage and other defect-assisted leakage mechanisms could all be important. Hole carrier velocity and impact ionisation were also studied in two batches of buried channel SiGe pMOSFET with x = 0.15 and x = 0.36, respectively. SiGe channel pMOSFETs were found to exhibit reduced impact ionisation compared to silicon control devices, which has been attributed to a strain-induced reduction of the density of states in the SiGe conduction and valence bands. Analysis of the hole carrier velocity indicated that pseudomorphic SiGe offered no performance enhancements over Si below 100 nm, possibly due to higher ion implantation damage and strain relaxation of the strained SiGe channel. The results indicate that velocity overshoot effects might not provide the performance improvements at short channel lengths that was previously hoped for

Investigation of the electrical properties of Si₁-xGex channel pMOSFETs with high-κ dielectrics

It is now apparent that the continued performance enhancements of silicon metal-oxide-semiconductor field effect transistors (MOSFETs) can no longer be met by scaling alone. High-mobility channel materials such as strained Si1-xGex and Ge are now being seriously considered to maintain the performance requirements specified by the semiconductor industry. In addition, alternative gate dielectric, or high-? dielectrics, will also be required to meet gate leakage requirements. This work investigates the properties of using strained Si1-xGex or Ge as alternative channel materials for pMOSFETs incorporating hafnium oxide (HfO2) high-? gate dielectric. Whilst the SiGe pMOSFETs (x = 0.25) exhibited an enhancement in hole mobility (300 K) over comparable silicon control pMOSFETs with sputtered HfO2 dielectric, high Coulomb scattering and surface roughness scattering relating to the dielectric deposition process meant that the effective hole mobilities were degraded with respect to the silicon universal curve. Germanium channel pMOSFETs with halo-doping and HfO2 gate dielectric deposited by atomic layer deposition showed high hole mobilities of 230 cm2V-1s-1 and 480 cm2V-1s-1 at room temperature and 77 K, respectively. Analysis of the off-state current for the Ge pMOSFETs over a range of temperatures indicated that band-to-band tunnelling, gate-induced drain leakage and other defect-assisted leakage mechanisms could all be important. Hole carrier velocity and impact ionisation were also studied in two batches of buried channel SiGe pMOSFET with x = 0.15 and x = 0.36, respectively. SiGe channel pMOSFETs were found to exhibit reduced impact ionisation compared to silicon control devices, which has been attributed to a strain-induced reduction of the density of states in the SiGe conduction and valence bands. Analysis of the hole carrier velocity indicated that pseudomorphic SiGe offered no performance enhancements over Si below 100 nm, possibly due to higher ion implantation damage and strain relaxation of the strained SiGe channel. The results indicate that velocity overshoot effects might not provide the performance improvements at short channel lengths that was previously hoped for.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Grandmothers’ care practices in areas of high deprivation of Scotland:the potential for health promotion

In many families grandparents play an essential role by providing secondary care for grandchildren. The family is a key setting for promoting children’s health; however, studies describing health initiatives with grandparents are rare. Grandparents could play an important role in promoting health for their grandchildren within their families and communities. The aim of this study was to examine the care practices of grandparents in families living in areas of high deprivation, and to consider the extent to which grandparents could be at the centre of health-promoting initiatives for children. A family practices approach was used to examine care practices within the framework of family resource (assets/capitals) use. In-depth interviews were carried out with grandmothers (n = 15) and mothers (n = 15) living in areas of high deprivation in Scotland. The results are presented as three economies of family living—political, moral and emotional. Grandparent care was described as a form of social capital, central to the wellbeing of the families, and enabled parents to access education and employment. Grandparent care was supported through families’ ability to access cultural amenities and green space (political). Grandparents’ care practices were described as either being responsible or fun (moral). Love appeared to be at the centre of grandparents’ care (emotional). The strengths and weaknesses of this framework were examined in relation to developing initiatives with grandparents. With further development work, grandparents could be the focus of health initiatives with their grandchildren with the support of appropriate policies and resources within their communities

Fractional quantum Hall states in a Ge quantum well

Measurements of the Hall and dissipative conductivity of a strained Ge quantum well on a SiGe/(001)Si substrate in the quantum Hall regime are reported. We analyse the results in terms of thermally activated quantum tunneling of carriers from one internal edge state to another across saddle points in the long range impurity potential. This shows that the gaps for different filling fractions closely follow the dependence predicted by theory. We also find that the estimates of the separation of the edge states at the saddle are in line with the expectations of an electrostatic model in the lowest spin-polarised Landau level (LL), but not in the spin-reversed LL where the density of quasiparticle states is not high enough to accommodate the carriers required

Loss of Atrx Affects Trophoblast Development and the Pattern of X-Inactivation in Extraembryonic Tissues

ATRX is an X-encoded member of the SNF2 family of ATPase/helicase proteins thought to regulate gene expression by modifying chromatin at target loci. Mutations in ATRX provided the first example of a human genetic disease associated with defects in such proteins. To better understand the role of ATRX in development and the associated abnormalities in the ATR-X (alpha thalassemia mental retardation, X-linked) syndrome, we conditionally inactivated the homolog in mice, Atrx, at the 8- to 16-cell stage of development. The protein, Atrx, was ubiquitously expressed, and male embryos null for Atrx implanted and gastrulated normally but did not survive beyond 9.5 days postcoitus due to a defect in formation of the extraembryonic trophoblast, one of the first terminally differentiated lineages in the developing embryo. Carrier female mice that inherit a maternal null allele should be affected, since the paternal X chromosome is normally inactivated in extraembryonic tissues. Surprisingly, however, some carrier females established a normal placenta and appeared to escape the usual pattern of imprinted X-inactivation in these tissues. Together these findings demonstrate an unexpected, specific, and essential role for Atrx in the development of the murine trophoblast and present an example of escape from imprinted X chromosome inactivation

"If I don't smoke shisha, I won't be able to sleep":Lived experiences of high school students in Ethiopia

BACKGROUND: Shisha smoking predisposes the users to cardiovascular diseases, cancer, and infections, such as tuberculosis, hepatitis, and herpes. In Ethiopia, there is little data on the adolescents’ shisha smoking experience. This study aimed to explore the lived experience of high school students and inform ongoing and future prevention and control interventions. METHODS: This study was conducted in Addis Ababa and Adama cities in Ethiopia. Twenty-five secondary school students aged 15-22 years who had shisha smoking experience participated in this study. A topic guide was used to facilitate the in-depth interviews (IDIs) and a digital audio recorder recorded the interviews. Interviews varied between 40-90 minutes and were conducted in private open-air spaces where only the interviewee and researcher were present. Each transcript was coded using Atlas.ti version 8 software. The analytical approach was iterative, with interview transcripts analyzed at the time of coding and re-analyzed after a preliminary result was drafted to search for additional themes. RESULTS: Students described two key factors that influenced their decision to initiate shisha smoking: peer influence and perceiving it as a means to release stress. After initiating shisha use students maintained the behaviour because of: peer influence, khat chewing, enjoyment of shisha smoking, having prolonged leisure time, and accessibility to shisha. Students regretted the impact shisha use had on their lives, such as conflict with their families, poor academic performance, and spending money on shisha smoking. Female students were also concerned about reproductive health risks related to shisha use. CONCLUSIONS: Peer influence played a major role both in initiating and maintaining shisha use. However, students admitted concern over the impact of shisha smoking on academic performance and their relationship with their families. Since shisha use is associated with khat chewing; shisha smoking control programs cannot be successful without controlling khat. Especially young girls had worries about their reproductive health risks associated with shisha use. This suggests that targeted awareness raising programs highlighting the dangers of shisha use for both health and safety; especially for young women is required

Democratising "Microscopi": a 3D printed automated XYZT fluorescence imaging system for teaching, outreach and fieldwork

Commercial fluorescence microscope stands and fully automated XYZt fluorescence imaging systems are generally beyond the limited budgets available for teaching and outreach. We have addressed this problem by developing “Microscopi”, an accessible, affordable, DIY automated imaging system that is built from 3D printed and commodity off-the-shelf hardware, including electro-mechanical, computer and optical components. Our design features automated sample navigation and image capture with a simple web-based graphical user interface, accessible with a tablet or other mobile device. The light path can easily be switched between different imaging modalities. The open source Python-based control software allows the hardware to be driven as an integrated imaging system. Furthermore, the microscope is fully customisable, which also enhances its value as a learning tool. Here, we describe the basic design and demonstrate imaging performance for a range of easily sourced specimens

Low Screening Rates Despite a High Prevalence of Significant Liver Fibrosis in People with Diabetes from Primary and Secondary Care

Diabetes is a driver of non-alcoholic fatty liver disease (NAFLD) and fibrosis. We determine current practices in examining liver fibrosis in people with diabetes and record prevalence levels in primary and secondary care. We extracted HbA(1c) results ≥48 mmol/mol to identify people with diabetes, then examined the proportion who had AST, ALT, and platelets results, facilitating calculation of non-invasive fibrosis tests (NIT), or an enhanced liver fibrosis score. Fibrosis markers were requested in only 1.49% (390/26,090), of which 29.7% (n = 106) had evidence of significant fibrosis via NIT. All patients at risk of fibrosis had undergone transient elastography (TE), biopsy or imaging. TE and biopsy data showed that 80.6% of people with raised fibrosis markers had confirmed significant fibrosis. We also show that fibrosis levels as detected by NIT are marginally lower in patients treated with newer glucose lowering agents (sodium-glucose transporter protein 2 inhibitors, dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists). In conclusion by utilising a large consecutively recruited dataset we demonstrate that liver fibrosis is infrequently screened for in patients with diabetes despite high prevalence rates of advanced fibrosis. This highlights the need for cost-effectiveness analyses to support the incorporation of widespread screening into national guidelines and the requirement for healthcare practitioners to incorporate NAFLD screening into routine diabetes care

Heteroepitaxial growth of ferromagnetic MnSb(0001) films on Ge/Si(111) virtual substrates

Molecular beam epitaxial growth of ferromagnetic MnSb(0001) has been achieved on high quality, fully relaxed Ge(111)/Si(111) virtual substrates grown by reduced pressure chemical vapor deposition. The epilayers were characterized using reflection high energy electron diffraction, synchrotron hard X-ray diffraction, X-ray photoemission spectroscopy, and magnetometry. The surface reconstructions, magnetic properties, crystalline quality, and strain relaxation behavior of the MnSb films are similar to those of MnSb grown on GaAs(111). In contrast to GaAs substrates, segregation of substrate atoms through the MnSb film does not occur, and alternative polymorphs of MnSb are absent