82 research outputs found
Preface to Symposium H: Post-Si-CMOS electronic devices: The role of Ge and III–V materials
No full textClose-to-Dirac point shift of large-area MOCVD-grown Bi2Te3’s Fermi level following growth on Sb2Te3
No full textWe developed a Metal Organic Chemical Vapour Deposition (MOCVD) process to grow the bi-layered Bi2Te3(top)/Sb2Te3 topological insulator on top of 4’’ Si(111). In single-phase Bi2Te3/Si(111), we have previously demonstrated clear topologically-protected surface states (TSS) by angle-resolved photoemission spectroscopy (ARPES) and magnetotransport, but a strong bulk contribution was still present with the Fermi level (EF) crossing the conduction band at ~0.5 eV above the Dirac point [1]. Following the growth of 90 nm Bi2Te3 in direct contact with 30 nm Sb2Te3, we observed by ARPES a remarkable shift of EF towards the Dirac point, totally suppressing the bulk states’ contribution. This was confirmed by magnetotransport, where, within the Hikami-Larkin-Nagaoka model, we measured an ideal α=-0.5 due to the optimized topologically-protected surface states. We will also present the first attempts in making use of such close-to-ideal positioning of the Bi2Te3’s Fermi level to manipulate magnetic figures in 2D-ferromagnet CrTe2 grown on top of the developed Bi2Te3/Sb2Te3/Si(111) heterostructure.
[1] L. Locatelli, A. Kumar, P. Tsipas, A. Dimoulas, E. Longo, R. Mantovan, "Magnetotransport and ARPES studies of the topological insulators Sb2Te3 and Bi2Te3 grown by MOCVD on large-area Si substrates" Scientific Reports 12, 3891 (2022).
*We acknowledge the Horizon 2020 project SKYTOP "Skyrmion-Topological Insulator and Weyl Semimetal Technology" (FETPROACT-2018-01, n. 824123)
Structural, electronic and transport properties of silicene and germanene
No full textstatus: Publishe
Chalkis. Urban expansion and development on both sides of Euripus Strait
No full textΕθνικό Μετσόβιο Πολυτεχνείο. Μεταπτυχιακή εργασία. Διεπιστημονικό - Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) "Αρχιτεκτονική - Σχεδιασμός του Χώρου : Πολεοδομία - Χωροταξία (Κατ. Β')
Strain balance approach for optimized signal-to-noise ratio in SiGe quantum well bolometers
No full textThis work presents thermal and electrical characterization of SiGe/Si multi-quantum wells (MQWs) with different layer profiles in complete bolometer structures. The thermal property of the bolometers was studied by measuring thermal coefficient of resistivity (TCR) through I-V curves for five temperatures (25, 40, 55, 80 and 100degC) and for four different pixel areas. The results show a strong dependency of TCR on the Si/SiGe layer thickness and the presence of dopant impurity in the MQW. The noise measurements of MQWs were performed carefully by eliminating all external contributions and the noise spectroscopy provided the noise characteristic parameters. The results demonstrate that the noise depends on the geometric size of the MQW and it increases with decreasing of the pixel area. The investigations show the noise level in the bolometer structures is sensitive to any dopant segregation from the contact layers
Magnetic skyrmion manipulation in CrTe2/WTe2 2D van der Waals heterostructure
No full textMagnetic skyrmions in two-dimensional van der Waals materials provide an ideal platform to push skyrmion technology to the ultimate atomically thin limit. In this work, we theoretically demonstrate the Dzyaloshinskii–Moriya interaction and the formation of a Néel-type skyrmion lattice at the CrTe2/WTe2 bilayer van der Waals heterostructure. Our calculations suggest a field-controlled Néel-type skyrmion lattice – ferromagnet transition cycle. In addition, a spin-torque induced by spin-polarized current injection was simulated in order to study the motion of a skyrmion on a racetrack, where an increase of the skyrmion Hall angle is observed at high temperatures. Consequently, this study suggests that generation and annihilation of skyrmions can be achieved with temperature or field control and also manipulate the velocity and the direction of the Néel-type skyrmions, through ultra-low current densities and temperature, thus, shedding light to the general picture of magnetic skyrmion control and design on two-dimensional van der Waals heterostructures.The following article has been accepted by Applied Physics Letters. After it is published, it will be found at https://doi.org/10.1063/5.0089999
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. and may be found at https://doi.org/10.1063/5.0089999.
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