The proliferation of van der Waals (vdW) heterostructures formed by stacking layered materials can accelerate scientific and technological advances. Here, we report a strategy for constructing vdW heterostructures through the interface engineering of the exfoliation substrate using a sub-5 nm polymeric film. Our construction method has two main features that distinguish it from existing techniques. First is the consistency of its exfoliation process in increasing the yield and in producing large (>10,000 μm²) monolayer graphene. Second is the applicability of its layer transfer process to different layered materials without requiring a specialized stamp—a feature useful for generalizing the assembly process. We demonstrate vdW graphene devices with peak carrier mobility of 200,000 and 800,000 cm² V⁻¹ s⁻¹ at room temperature and 9 K, respectively. The simplicity of our construction method and its versatility to different layered materials may open doors for automating the fabrication process of vdW heterostructures.

A scalable process that can yield low-resistance contacts to transition metal dichalcogenides is crucial for realizing a viable device technology from these materials. Here, we systematically examine the effect of high-k dielectric-mediated doping on key device metrics including contact resistance and carrier mobility. Specifically, we use top-gated transistors from monolayer MoS ₂ as a test vehicle and vary the MoS ₂ doping level by adjusting the amount of oxygen vacancies in the HfO _x gate dielectric. To understand the effect of doping on the contact resistance, from a fundamental standpoint, we first estimate the doping level in monolayer MoS2. The results of our device studies quantitatively show that the reduction in contact resistance with an increase in doping is due to the doping-induced lowering of the Schottky barrier height (SBH) at the metal-semiconductor interface. Furthermore, our temperature-dependent measurements reveal that a mixture of thermionic and field emissions, even at high carrier densities, dominates carrier conduction at the contact. While our study reveals the effectiveness of dielectric-induced doping in lowering SBH, it suggests that a further reduction of SBH using alternative methods is necessary for achieving an ohmic-like contact to monolayer MoS ₂ .

Tin dioxide (SnO₂) nanoparticles (NPs) can be applied in several ways due to their low cost, high surface-to-volume ratio, facile synthesis, and chemical stability. There is limited research on the biomedical application of SnO₂-based nanostructures. This study aimed to investigate the role of Zn doping in relation to the anticancer potential of SnO₂ NPs and to enhance the anticancer potential of SnO₂ NPs through Z doping. Pure SnO₂ and Zn-doped SnO₂ NPs (1% and 5%) were prepared using a modified sol–gel route. XRD, TEM, SEM, EDX, UV-Vis, FTIR, and PL techniques were used to characterize the physicochemical properties of produced NPs. XRD analysis revealed that the crystalline size and phase composition of pure SnO₂ increased after the addition of Zn. The spherical shape and homogenous distribution of these NPs were confirmed using TEM and SEM techniques. EDX analysis confirmed the Sn, Zn, and O elements in Zn-SnO₂ NPs without impurities. Zn doping decreased the band gap energy of SnO₂ NPs. The PL study indicated a reduction in the recombination rate of charges (electrons/holes) in SnO₂ NPs after Zn doping. In vitro studies showed that the anticancer efficacy of SnO₂ NPs increased with increasing levels of Zn doping in breast cancer MCF-7 cells. Moreover, pure and Zn-doped SnO₂ NPs showed good cytocompatibility in HUVECs. This study emphasizes the need for additional investigation into the anticancer properties of Zn-SnO2 nanoparticles in various cancer cell lines and appropriate animal models.

We study the effect of substrate coupling on the variability and the device characteristics of monolayer MoS ₂ field-effect transistors (FETs). Our electrical measurement results reveal significant improvements of key FET device metrics and marked reduction of device variability with reducing the interfacial energy. We attribute the observed improvements of the device characteristics to the reduction of the interface trap density and the suppression of the charged impurity scattering. This study establishes the critical role of substrate coupling on the performance and variability of monolayer MoS ₂ FETs.

SU-8 polymers are promising materials for various applications due to their low cost, excellent thermal stability, and outstanding mechanical properties. Cross-linking of SU-8 is a crucial process that determines the properties of the materials. This study investigates the effect of cross-linking of free-standing SU-8 films on optical transmission and PL emission under various curing conditions. Our findings show that an increase in the cross-linking density reduces optical transmission and causes a red shift of the PL emission band peaks. By directly measuring the optical response of the isolated SU-8, we remove any uncertainty due to the substrate’s presence. Moreover, we show that optical transmission and PL spectroscopy are two non-distractive techniques that can be employed to monitor the curing of the SU-8. This finding enhances our understanding of the cross-linking process in SU-8 and paves the way to further enhance the properties of the SU-8 polymer for various electronics and optoelectronics applications.