In this work, we report on the modification of electronic and magnetic properties of few layered graphene (FLG) nanoflakes via nitrogen functionalisation carried out using radio frequency (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N2 treatment leads to higher Ndoping levels in the FLGs (4.06 at%) as compared to the ECR process (2.18 at.%), the ferromagnetic behaviour of ECR FLG(118.62 x 10 -4 emu/gm) was significantly higher than the rf-PECVD (0.39 x 10 -4 emu/gm) and pristine graphene (3.47 x 10 -4 emu/gm). While both plasma processes introduce electron donating N-atoms in the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for each FLG type. While, the ECR plasma introduces more sp 2 type nitrogen moieties, the rf-PECVD process led to the formation of sp 3 coordinated nitrogen functionalities, as confirmed through Raman measurements. The samples further characterised using X -ray absorption near edge spectroscopy (XANES) and X-ray, ultraviolet photoelectron spectroscopies revealed an increased electronic density of states and a significantly higher concentration of pyrrolic groups in the rf-PECVD samples. Due to the formation of reactive edge structures and pyridinic nitrogen moieties, the ECR functionalised FLGs expressed highest saturation magnetisation behaviour with the lowest field hysteretic features. In comparison, the rf-PECVD samples, displayed the lowest saturation magnetisation owing to the disappearance of magnetic edge states and formation of stable non-radical type defects in the pyrrole type structures. Our experimental results thus provide new evidence to control the magnetic and electronic properties of few layered graphene nanoflakes via control of the plasma-processing route.• INTRODUCTIONIntrinsic magnetism observed in materials without d-or f-electrons has attracted much interest, especially for carbon-based materials and in particular, graphene. There has been a long-standing interest in the development of ferromagnetic graphene for realizing its applications into spintronic devices via the combination of spin and charge. [1][2][3][4] The introduction of magnetic response in graphene via the introduction of edges, vacancy defects or adsorbed atoms has been investigated using both theoretical and experimental means. [1][2][3][4][5][6][7][8][9][10][11][12][13] Various theoretical studies. [3][4][5][6][7][8][9][10] have suggested that zigzag edges or point defects in graphene as the spin units should 3 carry magnetic moment with possible long-range order coupling. This coupling itself can be ferromagnetic or antiferromagnetic, depending on whether the zigzag edges or defects correspond to the same or to different hexagonal sub-lattice of the graphene lattice, respectively. At present, the intrinsic magnetic properties of finite sized graphene sheet are far from being understood, given that the magnetic signal from a finite sized graphene sheet is too weak to be detected by macr...

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.

Two-dimensional (2D) van der Waals (vdW) crystals have attracted considerable interest for digital electronics beyond Si-based complementary metal oxide semiconductor technologies. Despite the transformative success of Si-based devices, there are limits to their miniaturization and functionalities. Here we realize a resonant tunnelling transistor (RTT) based on a 2D InSe layer sandwiched between two multilayered graphene (MLG) electrodes. In the RTT the energy of the quantum-confined 2D subbands of InSe can be tuned by the thickness of the InSe layer. By applying a voltage across the two MLG electrodes, which serve as the source and drain electrodes to the InSe, the chemical potential in the source can be tuned in and out of resonance with a given 2D subband, leading to multiple regions of negative differential conductance that can be additionally tuned by electrostatic gating. This work demonstrates the potential of InSe and InSe-based RTTs for applications in quantum electronics.

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.

Controlling the propagation and intensity of an optical signal is central to several technologies ranging from quantum communication to signal processing. These require a versatile class of functional materials with tailored electronic and optical properties, and compatibility with different platforms for electronics and optoelectronics. Here, the inherent optical anisotropy and mechanical flexibility of atomically thin semiconducting layers are investigated and exploited to induce a controlled enhancement of optical signals. This enhancement is achieved by straining and bending layers of the van der Waals crystal indium selenide (InSe) onto a periodic array of Si‐pillars. This enhancement has strong dependence on the layer thickness and is modelled by first‐principles electronic band structure theory, revealing the role of the symmetry of the atomic orbitals and light polarization dipole selection rules on the optical properties of the bent layers. The effects described in this paper are qualitatively different from those reported in other materials, such as transition metal dichalcogenides, and do not arise from a photonic cavity effect, as demonstrated before for other semiconductors. The findings on InSe offer a route to flexible nano‐photonics compatible with silicon electronics by exploiting the flexibility and anisotropic and wide spectral optical response of a 2D layered material.