1,064 research outputs found
Decoupling Graphene from SiC(0001) via Oxidation
When epitaxial graphene layers are formed on SiC(0001), the first carbon
layer (known as the "buffer layer"), while relatively easy to synthesize, does
not have the desirable electrical properties of graphene. The conductivity is
poor due to a disruption of the graphene pi-bands by covalent bonding to the
SiC substrate. Here we show that it is possible to restore the graphene
pi-bands by inserting a thin oxide layer between the buffer layer and SiC
substrate using a low temperature, CMOS-compatible process that does not damage
the graphene layer
Intermixing studies in GaN_1−xSb_x highly mismatched alloys
GaN1−xSbx with x~ 5-7% is a highly mismatched alloy predicted to have favorable properties for application as an electrode in a photo-electrochemical cell for solar water splitting. In this study, we grew GaN1−xSbx under conditions intended to induce phase segregation. Prior experiments with the similar alloy GaN1−xAsx, the tendency of Sb to surfact, and the low growth temperatures needed to incorporate Sb, all suggested that GaN1−xSbx alloys would likely exhibit phase segregation. We found that, except for very high Sb compositions, this was not the case, and that instead interdiffusion dominated. Characteristics measured by optical absorption were similar to intentionally grown bulk alloys for the same composition. Furthermore, the alloys produced by this method maintained crystallinity for very high Sb compositions, and allowed higher overall Sb compositions. This method may allow higher temperature growth while still achieving needed Sb compositions for solar water splitting applications
Phase stability of hafnium oxide and zirconium oxide on silicon substrate
Phase stabilities of Hf-Si-O and Zr-Si-O have been studied with
first-principles and thermodynamic modeling. From the obtained thermodynamic
descriptions, phase diagrams pertinent to thin film processing were calculated.
We found that the relative stability of the metal silicates with respect to
their binary oxides plays a critical role in silicide formation. It was
observed that both the HfO/Si and ZrO/Si interfaces are stable in a
wide temperature range and silicide may form at low temperatures, partially at
the HfO/Si interface.Comment: 5 pages, 3 figure
Tricuspid valve disease with significant tricuspid insufficiency in the fetus: Diagnosis and outcome
AbstractThe echocardiographic studies and clinical course of 27 fetuses (mean gestationl age 26.9 weeks) diagnosed in utero with tricuspid valve disease and significant tricuspid regurgitation were reviewed. The diagnosis of Ebstein's anomaly was made in 17 of the fetuses, 7 had tricuspid valve dysplasia with poorly developed but normally attached leaflets and 2 had an unguarded tricuspid valve orifice with little or no identifiable tricuspid tissue. One fetus was excluded from data analysis because a more complex heart lesion was documented at autopsy. All fetuses had massive right atrial dilation and most who were serially studied had progressive right-sided cardiomegaly. Hydrops fetalis was found in six cases and atrial flutter in five.Associated cardiac lesions included pulmonary stenosis in five cases and pulmonary alresia in six. Four fetuses with normal forward pulmonary artery flow at the initial examination were found at subsequent study to have retrograde pulmonary artery and ductal flow in association with the development of pulmonary stenosis (n = 1) and pulmonary atresia (n = 3). On review of the clinical course of the 23 fetuses (excluding 3 with elective abortion), 48% of the fetuses died in utero and 35% who were liveborn died despite vigorous medical and, when necessary, surgical management, many of whom had severe congestive heart failure. Of the four infants who survived the neonatal period, three had a benign neonatal course, all of whom were diagnosed with mild to moderate Ebstein's anomaly; only one had pulmonary outflow obstruction. An additional finding at autopsy was significant lung hypoplasia documented in 10 of 19 autopsy reports.Tricuspid valve anomalies with tricuspid insufficiency can be identified echocardiographically in the fetus and should be searched for in the presence of right atrial enlargement. The prognosis for the fetus diagnosed in utero with significant tricuspid valve disease is extremely poor, with a prenatal course that includes progressive right heart dilation, with cardiac failure and lung hypoplasia in many and development of pulmonary stenose or pulmonary atresia later in gestation in some
Personalized Palliative and Survivorship Care for Patients With Metastatic Cancer Treated With Radiation Therapy
While the benefits of early palliative care for patients with metastatic cancer are well established, cancer survivorship remains inadequately integrated into the care of patients with distant metastases. Moreover, the optimal model of care delivery is poorly defined. A prognostic model previously developed and validated at Good Samaritan University Hospital identified four groups of patients with metastatic solid tumor malignancy having very favorable, favorable, standard or unfavorable prognoses with median survival of 31, 14, 4 and 1 month, respectively. This framework holds promise for the personalized delivery of supportive, palliative and survivorship care services in the context of radiation therapy. We review the published literature providing the rationale for a novel multidisciplinary care model where the radiation oncology Clinical Nurse Specialist identifies and coordinates interventions to address unmet physical and emotional issues faced by survivors with metastatic cancer with the goal of improving quality of life and overall survival
Statistical Mechanics of the Vicinal Surfaces with Adsorption
We study the vicinal surface with adsorption below the roughening
temperature, using the restricted solid-on-solid model coupled with the Ising
model. By the product-wavefunction renormalization group method, we calculate
the surface gradient and the adsorption coverage as a function of
the Andreev field which makes surface tilt. Combining Monte Carlo
calculations, we show that there emerges effective attraction between the
steps. This attractive interaction leads to instability against step bunching.Comment: 10 pages, 4 figures, ISSI PDSC-2000, submitted to Surf. Sci. RevTeX
3.1 preprint styl
Medium Energy Ion Scattering of Gr on SiC(0001) and Si(100)
Depth profiling of graphene with high-resolution ion beam analysis is a
practical method for analysis of monolayer thicknesses of graphene. Not only is
the energy resolution sufficient to resolve graphene from underlying SiC, but
by use of isotope labeling it is possible to tag graphene generated from
reacted ethylene. Furthermore, we are able to analyze graphene supported by
oxidized Si(100) substrates, allowing the study of graphene films grown by
chemical vapor deposition on metal and transfered to silicon. This introduces a
powerful method to explore the fundamentals of graphene formation
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