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Michael Altvater

Publications and source records attributed to Michael Altvater.

3 recordsLinked to original sources

Indium selenides for next-generation low-power computing devices

As silicon-based computing approaches fundamental physical limits in energy efficiency, speed, and density, the search for complementary materials to extend or replace CMOS technology has become increasingly urgent. While two-dimensional (2D) transition metal dichalcogenides have been extensively investigated, van der Waals indium selenides--particularly InSe and In2Se3--offer a compelling alternative with distinct advantages for next-generation electronics. Unlike conventional 2D semiconductors, indium selenides combine exceptional electron mobility (exceeding 1,000 cm^2V^-1s^-1), high thermal velocity (>2x10^7 cm/s), thickness-tunable bandgaps (0.97-2.5 eV), and unique phase-dependent ferroelectric properties, enabling both high-performance logic and non-volatile memory functions within a single material system. This perspective critically evaluates the materials properties, fabrication challenges, and device applications of indium selenides, examining their potential to surpass silicon in ultra-scaled transistors through ballistic transport while simultaneously offering ferroelectric memory capabilities impossible in conventional semiconductors. We analyze recent breakthroughs in ballistic InSe transistors, tunnel field-effect transistors, and In2Se3-based ferroelectric devices for information storage, and identify key research priorities for addressing persistent challenges in scalable synthesis, phase control, and oxidation prevention. By bridging fundamental materials science with practical device engineering, we provide a roadmap for translating the exceptional properties of indium selenides into commercially viable, low-power computing technologies that can overcome the limitations of silicon while enabling novel computing architectures.

cond-mat.mtrl-sci

Revealing the Charge Density Wave Proximity Effect in Graphene on 1T-TaS$_2$

The proximity-effect, whereby materials in contact appropriate each others electronic-properties, is widely used to induce correlated states, such as superconductivity or magnetism, at heterostructure interfaces. Thus far however, demonstrating the existence of proximity-induced charge-density-waves (PI-CDW) proved challenging. This is due to competing effects, such as screening or co-tunneling into the parent material, that obscured its presence. Here we report the observation of a PI-CDW in a graphene layer contacted by a 1T-TaS2 substrate. Using scanning tunneling microscopy (STM) and spectroscopy (STS) together with theoretical-modeling, we show that the coexistence of a CDW with a Mott gap in 1T-TaS2 coupled with the Dirac-dispersion of electrons in graphene, makes it possible to unambiguously demonstrate the PI-CDW by ruling out alternative interpretations. Furthermore, we find that the PI-CDW is accompanied by a reduction of the Mott gap in 1T-TaS2 and show that the mechanism underlying the PI-CDW is well-described by short-range exchange-interactions that are distinctly different from previously observed proximity effects.

cond-mat.mes-hall

Two-step conversion of metal and metal oxide precursor films to 2D transition metal dichalcogenides and heterostructures

From the laboratory to real-world applications, synthesis of two dimensional (2D) materials requires modular techniques to control morphology, structure, chemistry, and the plethora of exciting properties arising from these nanoscale materials. In this review, we explore one of the many available synthesis techniques; the extremely versatile two-step conversion (2SC) method. The 2SC technique relies on deposition of a metal or metal oxide film, followed by reaction with a chalcogen vapor at an elevated temperature, converting the precursor film to a crystalline transition metal dichalcogenide (TMD). Herein, we consider the variables at each step of the 2SC process including the impact of the precursor film material and deposition technique, the influence of gas composition and temperature during conversion, as well as other factors controlling high quality 2D TMD synthesis. We feature the specific advantages to the 2SC approach including deposition on diverse substrates, low temperature processing, orientation control, and heterostructure synthesis, among others. Finally, emergent opportunities that take advantage of the 2SC approach are discussed to include next generation electronics, sensing, and optoelectronic devices as well as catalysis for energy-related applications; spotlighting the great potential of the 2SC technique.

cond-mat.mtrl-sci