RESUMEN
In this study, we present a full characterization of the electronic properties of phase change material (PCM) double-layered heterostructures deposited on silicon substrates. Thin films of amorphous Ge-rich Ge-Sb-Te (GGST) alloys were grown by physical vapor deposition on Sb2Te3 and on Ge2Sb2Te5 layers. The two heterostructures were characterized in situ by X-ray and ultraviolet photoemission spectroscopies (XPS and UPS) during the formation of the interface between the first and the second layer (top GGST film). The evolution of the composition across the heterostructure interface and information on interdiffusion were obtained. We found that, for both cases, the final composition of the GGST layer was close to Ge2SbTe2 (GST212), which is a thermodynamically favorable off-stoichiometry GeSbTe alloy in the Sb-GeTe pseudobinary of the ternary phase diagram. Density functional theory calculations allowed us to calculate the density of states for the valence band of the amorphous phase of GST212, which was in good agreement with the experimental valence bands measured in situ by UPS. The same heterostructures were characterized by X-ray diffraction as a function of the annealing temperature. Differences in the crystallization process are discussed on the basis of the photoemission results.
RESUMEN
A suitable way to modify the electronic properties of graphene-while maintaining the exceptional properties associated with its two-dimensional (2D) nature-is its functionalisation. In particular, the incorporation of hydrogen isotopes in graphene is expected to modify its electronic properties leading to an energy gap opening, thereby rendering graphene promising for a widespread of applications. Hence, deuterium (D) adsorption on free-standing graphene was obtained by high-energy electron ionisation of D2 and ion irradiation of a nanoporous graphene (NPG) sample. This method allows one to reach nearly 50 at.% D upload in graphene, higher than that obtained by other deposition methods so far, towards low-defect and free-standing D-graphane. That evidence was deduced by X-ray photoelectron spectroscopy of the C 1s core level, showing clear evidence of the D-C sp3 bond, and Raman spectroscopy, pointing to remarkably clean and low-defect production of graphane. Moreover, ultraviolet photoelectron spectroscopy showed the opening of an energy gap in the valence band. Therefore, high-energy electron ionisation and ion irradiation is an outstanding method for obtaining low defect D-NPG with a high D upload, which is very promising for the fabrication of semiconducting graphane on large scale.
RESUMEN
Background: Cardiovascular disease is a frequent complication of type 1 diabetes (T1D). We evaluated the effectiveness of switching from glargine to degludec in reducing the cardiovascular risk factors, the Framingham risk score (FRS) and visceral adiposity index (VAI) in patients with T1D and autoimmune polyglandular syndrome (APS). Methods: We selected 66 T1D outpatients who had been on stable treatment with glargine for at least 5 years. Among them, 30 patients maintained glargine (group A), while 36 were switched to degludec (group B) for 12 months. At baseline and after 12 months of observation, clinical and metabolic parameters, insulin dose, 30-days blood glucose (BG) self monitoring, VAI and FRS were obtained. Results: At baseline, patients in group B had more hypoglycaemic episodes and prevalence of hypertension than those in group A. After 12 months on degludec, patients in group B had a significant decrease in BMI (p = 0.003), waist circumference (p < 0.001), total daily insulin as U/day and U/kg (p = 0.001 for both), basal insulin as U/day and U/kg (p = 0.001 for both), HbA1c (p < 0.001), mean (p = 0.035) and standard deviation of daily BG (p = 0.017), mean pre-meal BG (p = 0.016), number of hypoglycaemic episodes (p = 0.001), VAI (p = 0.012) and FRS (p = 0.019) and a significant increase in HDL-C (p < 0.001), compared to baseline. At 12 months of treatment a significant decrease in BMI (p = 0.017), WC (p = 0.003), SBP (p = 0.001), DBP (p = 0.005), basal insulin as U/day (p = 0.018) and U/kg (p = 0.045), HbA1c (p = 0.040) and FRS (p = 0.010) was observed in group B compared to group A. Conclusions: Our preliminary data suggest that 12 months' treatment with degludec is associated with an improvement of glycaemic control, cardiometabolic and cardiovascular risk, compared to glargine, in patients with T1D and APS.