Black phosphorus (BP) is a layered semiconductor with a high mobility of up to ∼1000 cm² V⁻¹s⁻¹ and a narrow bandgap of ∼0.3 eV, and shows potential applications in thermoelectrics. In stark contrast to most other layered materials, electrical and thermoelectric properties in the basal plane of BP are highly anisotropic. To elucidate the mechanism for such anisotropy, we fabricated BP nanoribbons (∼100 nm thick) along the armchair and zigzag directions, and measured the transport properties. It is found that both the electrical conductivity and Seebeck coefficient increase with temperature, a behavior contradictory to that of traditional semiconductors. The three-dimensional variable range hopping model is adopted to analyze this abnormal temperature dependency of electrical conductivity and Seebeck coefficient. The hopping transport of the BP nanoribbons, attributed to high density of trap states in the samples, provides a fundamental understanding of the anisotropic BP for potential thermoelectric applications.

Two-dimensional transition metal dichalcogenides have demonstrated potential for advanced electrical and optoelectronic applications. For these applications, it is necessary to modify their electrical or optoelectronic properties. Doping is one of the most prevalent techniques to modify the band structure of semiconductor materials. Herein, we report the p-type doping effect on few-layer and multi-layer MoS₂ that are selectively decorated with Ag nanoparticles via laser-assisted direct photoexcitation of MoS₂ exposed in AgNO₃ solution. This method can control the doping level by varying the duration of the laser irradiation, which is confirmed by the observed gradual rise of MoS₂ device channel resistance and photoluminescence spectra enhancement. This study demonstrated a simple, controllable, and selective doping technique using laser-assisted photo-reduction.

Cd_xZn_1−xO alloys, as a transparent conducting oxide, have recently attracted much attention for potential optoelectronic applications. In this letter, we report a hydrostatic pressure-induced phase transition of Cd_xZn_1−xO alloys from the wurtzite to the rocksalt structure and its phase diagram probed using a diamond anvil cell. It is found that the transition pressure, determined by changes in optical and structural properties, depends sensitively on the composition. As the Cd content increases, the critical pressure decreases, until at x = 0.67 where the alloy is intrinsically stable in the rocksalt phase even at ambient pressure. The wurtzite phase is light emitting with a direct bandgap that slightly widens with increasing pressure, while the rocksalt phase has a much wider bandgap that is indirect. The pressure-sensitive light emission and phase transition may find potential applications in fields such as stress sensing and energy storage.

We present a method for nanoscale thermal imaging of insulating thin films using atomic force microscopy (AFM), and we demonstrate its utility on VO₂. We sweep the applied voltage V to a conducting AFM tip in contact mode and measure the local current I through the film. By fitting the IV curves to a Poole–Frenkel conduction model at low V, we calculate the local temperature with spatial resolution better than 50 nm using only fundamental constants and known film properties. Our thermometry technique enables local temperature measurement of any insulating film dominated by the Poole–Frenkel conduction mechanism and can be extended to insulators that display other conduction mechanisms.

Point defect equilibration in nanocrystalline hafnium oxide thin films in the monoclinic $\left({\text{m-HfO}}_2\right)$ phase was studied by electrochemical measurements performed under varying temperature and oxygen partial pressure $\left(P_{{\text{O}}_2}\right)$ on films of 35–63 nm thickness on single crystal MgO and ${\text{Al}}_2{\text{O}}_3$ substrates. The conductance varied as ${\left(P_{{\text{O}}_2}\right)}^n$ , where $n$ is the in the range $\sim +1/11$ to $\sim +1/14$ , at high $P_{{\text{O}}_2}$ . The increasing conductance with $P_{{\text{O}}_2}$ suggests that the electronic conduction in the ${\text{HfO}}_2$ films is p-type and oxygen interstitials or hafnium vacancies, rather than oxygen vacancies, could be dominant charged point defects in nanocrystalline, undoped ${\text{m-HfO}}_2$ films.