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2D semiconductors are promising candidates for next generation electronics and optoelectronics. However, their exposure to air and/or resists during device fabrication can cause considerable degradation of material quality, hindering their study and exploitation. Here, field effect transistors (FETs) are designed and fabricated by encapsulation of the 2D semiconductor indium selenide (InSe) with alumina (Al2O3) and by self‐aligned electrical contacts. The Al2O3‐film is grown directly on InSe immediately after its exfoliation to provide a protecting capping layer during and after device fabrication. The InSe‐FETs exhibit a high electron mobility of up to ≈103 cm2 V−1 s−1 at room temperature for a 4‐nm‐thick InSe layer, a low contact resistance (down to 0.18 kΩ) and a high, fast, and broad‐band photoresponsivity. The photoresponsivity depends on the InSe‐layer thickness and photon wavelength, reaching a value of up to 108 A W−1 in the visible spectral range, at least one order of magnitude larger than previously reported for similar photodetectors. The proposed fabrication is scalable and suitable for high‐precision pattern definition. It could be extended to other 2D materials and multilayer structures where alumina could also provide effective screening of the electric field induced by polar molecules and/or charged impurities present near the surface of the 2D layer. [ABSTRACT FROM AUTHOR]

The ability of a material to conduct heat influences many physical phenomena, ranging from thermal management in nanoscale devices to thermoelectrics. Van der Waals 2D materials offer a versatile platform to tailor heat transfer due to their high surface‐to‐volume ratio and mechanical flexibility. Here, the nanoscale thermal properties of 2D indium selenide (InSe) are studied by scanning thermal microscopy. The high electrical conductivity, broad‐band optical absorption, and mechanical flexibility of 2D InSe are accompanied by an anomalous low thermal conductivity (κ). This can be smaller than that of low‐κ dielectrics, such as silicon oxide, and it decreases with reducing the lateral size and/or thickness of InSe. The thermal response is probed in free‐standing InSe layers as well as layers supported by a substrate, revealing the role of interfacial thermal resistance, phonon scattering, and strain. These thermal properties are critical for future emerging technologies, such as field‐effect transistors that require efficient heat dissipation or thermoelectric energy conversion with low‐κ, high electron mobility 2D materials, such as InSe. [ABSTRACT FROM AUTHOR]

Abstract: The controlled manipulation of the spin and charge of electrons in a semiconductor has the potential to create new routes to digital electronics beyond Moore's law, spintronics, and quantum detection and imaging for sensing applications. These technologies require a shift from traditional semiconducting and magnetic nanostructured materials. Here, a new material system is reported, which comprises the InSe semiconductor van der Waals crystal that embeds ferromagnetic Fe‐islands. In contrast to many traditional semiconductors, the electronic properties of InSe are largely preserved after the incorporation of Fe. Also, this system exhibits ferromagnetic resonances and a large uniaxial magnetic anisotropy at room temperature, offering opportunities for the development of functional devices that integrate magnetic and semiconducting properties within the same material system. [ABSTRACT FROM AUTHOR]

The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the "post‐transition" metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n‐type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light‐induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate‐controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light‐induced charge transfer in gate‐tunable InSe/graphene phototransistors for optoelectronics and quantum metrology. InSe‐capped graphene field effect transistors combine the photosensitivity of InSe with the unique electrical properties of graphene. The light‐induced charge transfer at the InSe/graphene interface can induce an increase or decrease of the carrier density in graphene and a light‐induced transition from a hole‐ to an electron‐carrier current, with potential for quantum metrology and miniaturized optical sensors and switches. [ABSTRACT FROM AUTHOR]