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To achieve the commercialization of two-dimensional (2D) semiconductors, the identification of an appropriate combination of 2D semiconductors and three-dimensional (3D) metals is crucial. Furthermore, understanding the van der Waals (vdW) interactions between these materials in thin-film semiconductor processes is essential. Optimizing these interactions requires precise control over the properties of the vdW interface through specific pre- or post-treatment methods. This study utilizes Se-environment annealing as a post-treatment technique, which allows for modification of the vdW gap distance and enhancement of the stability of the interfacial structure through the process of Se intercalation and deintercalation at the 2D-3D interface. The depth of Se intercalation and deintercalation is adjusted by varying the temperature and duration of the postannealing process in an Se environment. This precise control over the process enables the effective metallization of 2D semiconductors. The results indicate that expanding the vdW gap and stabilizing the interface structure through this post-treatment significantly improve the metal contact properties in devices such as field-effect transistors and photovoltaic Schottky diodes by minimizing metal-induced gap states, thus reducing Fermi level pinning. The application of Se intercalation and deintercalation techniques achieves an exceptionally low contact resistance of 773 Ω·μm between p-type WSe2 and Au. Additionally, the integration of doping-free WSe2 complementary metal-oxide-semiconductor (CMOS) circuits using Se-environment annealing and blocking layers is demonstrated, establishing a promising advancement in semiconductor technology.

Topological insulators have recently received attention in optoelectronic devices because of their high mobility and broadband absorption resulting from their topological surface states. In particular, theoretical and experimental studies have emerged that can improve the spin generation efficiency in a topological insulator‐based p–n junction structure called a TPNJ, drawing attention in optospintronics. Recently, research on implementing the TPNJ structure is conducted; however, studies on the device characteristics of the TPNJ structure are still insufficient. In this study, the TPNJ structure is effectively implemented without intermixing by controlling the annealing temperature, and the photocharacteristics appearing in the TPNJ structure are investigated using a cross‐pattern that can compare the characteristics in a single device. Enhanced photo characteristics are observed for the TPNJ structure. An optical pump Terahertz probe and a physical property measurement system are used to confirm the cause of improved photoresponsivity. Consequently, the photocharacteristics are improved owing to the change in the absorption mechanism and surface transport channel caused by the Fermi level shift in the TPNJ structure. [ABSTRACT FROM AUTHOR]

Topological materials have significant potential for spintronic applications owing to their superior spin–charge interconversion. Here, the spin‐to‐charge conversion (SCC) characteristics of epitaxial Bi1−xSbx films is investigated across the topological phase transition by spintronic terahertz (THz) spectroscopy. An unexpected, intense spintronic THz emission is observed in the topologically nontrivial semimetal Bi1−xSbx films, significantly greater than that of Pt and Bi2Se3, which indicates the potential of Bi1−xSbx for spintronic applications. More importantly, the topological surface state (TSS) is observed to significantly contribute to SCC, despite the coexistence of the bulk state, which is possible via a unique ultrafast SCC process, considering the decay process of the spin‐polarized hot electrons. This means that topological material‐based spintronic devices should be fabricated in a manner that fully utilizes the TSS, not the bulk state, to maximize their performance. The results not only provide a clue for identifying the source of the giant spin Hall angle of Bi1−xSbx, but also expand the application potential of topological materials by indicating that the optically induced spin current provides a unique method for focused‐spin injection into the TSS. [ABSTRACT FROM AUTHOR]

The interfacial electronic structures of a bilayer of fullerene (C60) and zinc phthalocyanine (ZnPc) grown on vanadium pentoxide (V2O5) thin films deposited using radio frequency sputtering under various conditions were studied using X-ray and ultraviolet photoelectron spectroscopy. The energy difference between the highest occupied molecular orbital (HOMO) level of the ZnPc layer and the lowest unoccupied molecular orbital (LUMO) level of the C60 layer was determined and compared with that grown on an indium tin oxide (ITO) substrate. The energy difference of a heterojunction on all V2O5 was found to be 1.3~1.4 eV, while that on ITO was 1.1 eV. This difference could be due to the higher binding energy of the HOMO of ZnPc on V2O5 than that on ITO regardless of work functions of the substrates. We also determined the complete energy level diagrams of C60/ZnPc on V2O5 and ITO. [ABSTRACT FROM AUTHOR]

The effects of oxidation on strain relaxation in Si1-xGex layers on silicon substrates were investigated. Si1-xGex layers, with different Ge fractions (x=0.15 and 0.3), were grown on chemically cleaned silicon substrates by an ultrahigh vacuum chemical vapor deposition process. Oxidation at 800 and 900 °C under O2 ambient in a tube furnace resulted in the production of silicon oxide layers on top and a Ge-rich region in the Si1-xGex films. It was observed that the oxidation of Si0.85Ge0.15 films at 900 °C produced the relaxation of the misfit strain in the remnant Si1-xGex layer and the increase in strain in the Ge pile-up layer with increasing oxidation time, while the oxidation at 800 °C produced no changes in the misfit strain in the Si1-xGex layers. The oxidation of Si0.70Ge0.30 films at 800 °C showed the relaxation of the misfit strain in the remnant Si1-xGex layer with the accumulation of stain in the Ge pile-up layer. However, the oxidation of Si0.70Ge0.30 layers at 900 °C exhibited the strain relaxation in the Ge pile-up layer after the Ge pile-up was extended into the remaining Si1-xGex layer, with the formation of misfit dislocations at the interface between the remaining Si1-xGex and Si substrate. [ABSTRACT FROM AUTHOR]

Changes in the electrical properties and thermal stability of HfO 2 grown on Al 2 O 3 -passivated InSb by atomic layer deposition (ALD) were investigated. The deposited HfO 2 on InSb at a temperature of 200 °C was in an amorphous phase with low interfacial defect states. During post-deposition annealing (PDA) at 400 °C, In-Sb bonding was dissociated and diffusion through HfO 2 occurred. The diffusion of indium atoms from the InSb substrate into the HfO 2 increased during PDA at 400 °C. Most of the diffused atoms reacted with oxygen in the overall HfO 2 layer, which degraded the capacitance equivalent thickness (CET). However, since a 1-nm-thick Al 2 O 3 passivation layer on the InSb substrate effectively reduced the diffusion of indium atoms, we could significantly improve the thermal stability of the capacitor. In addition, we could dramatically reduce the gate leakage current by the Al 2 O 3 passivation layer. Even if the border traps measured by C-V data were slightly larger than those of the as-grown sample without the passivation layer, the interface trap density was reduced by the Al 2 O 3 passivation layer. As a result, the passivation layer effectively improved the thermal stability of the capacitor and reduced the interface trap density, compared with the sample without the passivation layer.