Top Gate Contact Research Articles

Electrically tunable quantum emitters in an ultrathin graphene–hexagonal boron nitride van der Waals heterostructure

We explore the photoluminescence (PL) properties of hexagonal boron nitride (h-BN) quantum emitters embedded within atomically thin graphene/h-BN heterostructures fabricated by mechanical transfer. Stable light emission could be observed from h-BN emitters which due to the local presence of multilayer h-BN are not subject to fluorescence quenching by graphene. By using graphene as a top gate contact, the PL emission can be tuned by up to 24 meV per V/nm, with a high robustness of the emitters over several voltage sweep cycles. Two different types of h-BN emitters were observed, one with a quadratic and the other one with a linear Stark shift. Moreover, the vertical electric field leads to an asymmetric modulation of both the fluorescence intensity and lifetime between the negative and positive gate voltage regimes. The overall behavior can be well explained by a model involving different rates for electron and hole tunneling between the h-BN and graphene layers. Our findings suggest ultrathin van der Waals heterostructures as valuable platforms for fine tuning the optoelectronic properties of atomic defect-based quantum emitters.

Characteristics of Organic TFTs with PBTTT-C12 as polymeric semiconductor layer

In the fabrication process of OTFTs is necessary to focus on the electrical properties of channel’s materials to improve its behavior and then exploit the use of this technology in different applications. For this reason, this paper was focused into studying the electrical behavior of OTFTs made with PBTTT instead of P3HT OTFT process. Furthermore, two different contacts configuration were also included. The OTFT’s structure used in this work was upper drain and source contacts / top gate contact. In addition, OTFTs output characterizations were measured and their physical-electrical parameters, as mobility and threshold voltage, were extracted by UMEM method. Good agreement in output characteristics was obtained between experimental data and modeled extracted data. Finally, after one month, a degradation of less than 5 % of the output characteristics was observed.

Schottky barrier source-gated ZnO thin film transistors by low temperature atomic layer deposition

We have fabricated ZnO source-gated thin film transistors (SGTFTs) with a buried TiW source Schottky barrier and a top gate contact. The ZnO active channel and thin high-κ HfO2 dielectric utilized are both grown by atomic layer deposition at temperatures less than 130 °C, and their material and electronic properties are characterized. These SGTFTs demonstrate enhancement-mode operation with a threshold voltage of 0.91 V, electron mobility of 3.9 cm2 V−1 s−1, and low subthreshold swing of 192 mV/decade. The devices also exhibit a unique combination of high breakdown voltages (>20 V) with low output conductances.