The van der Waals heterostructures have evolved as novel materials for complementing the Si-based semiconductor technologies. Group-10 noble metal dichalcogenides (e.g., PtS₂, PtSe₂, PdS₂, and PdSe₂) have been listed into two-dimensional (2D) materials toolkit to assemble van der Waals heterostructures. Among them, PdSe₂ demonstrates advantages of high stability in air, high mobility, and wide tunable bandgap. However, the regulation of p-type doping of PdSe₂ remains unsolved problem prior to fabricating p–n junction as a fundamental platform of semiconductor physics. Besides, a quantitative method for the controllable doping of PdSe₂ is yet to be reported. In this study, the doping level of PdSe₂ was correlated with the concentration of Lewis acids, for example, SnCl₄, used for soaking. Considering the transfer characteristics, the threshold voltage (the gate voltage corresponding to the minimum drain current) increased after SnCl₄ soaking treatment. PdSe₂ transistors were soaked in SnCl₄ solutions with five different concentrations. The threshold voltages from the as-obtained transfer curves were extracted for linear fitting to the threshold voltage versus doping concentration correlation equation. This study provides in-depth insights into the controllable p-type doping of PdSe₂. It may also push forward the research of the regulation of conductivity behaviors of 2D materials.

Carbon nanotubes (CNTs) have attracted great attentions in the field of electronics, sensors, healthcare, and energy conversion. Such emerging applications have driven the carbon nanotube research in a rapid fashion. Indeed, the structure control over CNTs has inspired an intensive research vortex due to the high promises in electronic and optical device applications. Here, this in-depth review is anticipated to provide insights into the controllable synthesis and applications of high-quality CNTs. First, the general synthesis and post-purification of CNTs are briefly discussed. Then, the state-of-the-art electronic device applications are discussed, including field-effect transistors, gas sensors, DNA biosensors, and pressure gauges. Besides, the optical sensors are delivered based on the photoluminescence. In addition, energy applications of CNTs are discussed such as thermoelectric energy generators. Eventually, future opportunities are proposed for the Internet of Things (IoT) oriented sensors, data processing, and artificial intelligence.

We demonstrate the selective detection of hydrogen sulfide at breath concentration levels under humid airflow, using a self-validating 64-channel sensor array based on semiconducting single-walled carbon nanotubes (sc-SWCNTs). The reproducible sensor fabrication process is based on a multiplexed and controlled dielectrophoretic deposition of sc-SWCNTs. The sensing area is functionalized with gold nanoparticles to address the detection at room temperature by exploiting the affinity between gold and sulfur atoms of the gas. Sensing devices functionalized with an optimized distribution of nanoparticles show a sensitivity of 0.122%/part per billion (ppb) and a calculated limit of detection (LOD) of 3 ppb. Beyond the self-validation, our sensors show increased stability and higher response levels compared to some commercially available electrochemical sensors. The cross-sensitivity to breath gases NH₃ and NO is addressed demonstrating the high selectivity to H₂S. Finally, mathematical models of sensors’ electrical characteristics and sensing responses are developed to enhance the differentiation capabilities of the platform to be used in breath analysis applications.

Chemical modification and vertical stacking of two-dimensional materials are promising techniques for new nanoelectronic devices. We present Density Functional Tight Binding (DFTB) calculations of a field-effect device, based on lateral and vertical heterostructures of 2D materials. The device consists of a phosphorene channel protected by graphene sheets, which work as contacts and are divided into the source and drain by local hydrogenation of graphene, which gives insulating graphane. In this device composed of only 3 layers, single sheets of graphene-graphane can work as both leads and oxide gate, while also acting as protective layers for a phosphorene channel. We show how for perfect vdW heterostructures of graphane/phosphorene/graphane and graphene/phosphorene/graphene the Schottky barrier is deeply influenced by normal electric fields, and we characterize electronic transport of such a device. Finally, we characterize phosphorene channel doping and defects, which, at very high densities in the transport direction, enables transport inside the phosphorene bandgap.