Cd x Hg1–x Se alloy nanocrystals are obtained from CdSe semiconductor nanocrystals via cation exchange. By varying the composition during the exchange process, the Cd x Hg1–x Se alloy nanocrystals offer a widely tunable electronic transition from visible to NIR and even to mid-IR range. The visible bandgap transition of the CdSe colloidal quantum dot gradually red-shifts to the near-IR with the addition of the Hg precursor, and then the steady-state intraband (or intersub-band) transition of the Cd x Hg1–x Se alloy nanocrystals appears. Finally, as the electron density is increased by successive addition of metal precursor, localized surface plasmon resonances (LSPRs) appear as a major electronic transition in the mid-IR regime. The shift of the major electronic transition from the bandgap to LSPRs infers that the exciton spatially moves to the surface from the inside of the nanocrystal through the cation change and further crystal growth. The corresponding variance of the nanocrystals’ structural, compositional, optical, electrical, and magnetic properties was carefully monitored by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron-dispersive X-ray (EDS) spectroscopy, time-resolved photoluminescence, photocurrent measurement, and electron paramagnetic resonance (EPR) spectroscopy, respectively. While a shift in only the bandgap has been observed in conventional quantum dots when cation-exchanged, the major oscillating transition transfers from the bandgap to the higher quantum states in Cd x Hg1–x Se alloy nanocrystal formed by the cation-exchange in this report. The compositional change expanding the optical range of nanocrystals from visible to mid-IR regime will provide a useful means of optimally tuning the electronic transition of nanocrystal-based applications along with improved optical selectivity demonstrated by a single intraband or LSPR peak.

Air-stable, ambipolar heterojunction-based organic light-emitting field-effect transistors (OLEFETs) with a top-contact, multidigitated, long-channel geometry were produced, and the current–voltage–light emission (I–V–L) characteristics were systematically examined. Two active layers of p-type pentacene and n-type N,N′-ditridecylperylene-3,4,9,10-tetra carboxylic diimide (P13) as well as a protecting layer of 2,5-bis(4-biphenyl) thiophene (BP1T) were successively deposited using the neutral cluster beam deposition method. On the basis of the growth of high-quality, well-packed crystalline thin films, the OLEFETs demonstrated good field-effect characteristics, well-balanced ambipolarity, operational stability, and electroluminescence (EL) under ambient conditions. The operating conduction and EL mechanisms responsible for the observed recombination zone are discussed with the aid of light-emission images obtained using a charge-coupled device.

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Realization of size controllable graphene micro/nanogap with a micro/nanowire mask method for organic fieldeffect transistors Appl. Phys. Lett. 99, 103301 (2011); 10.1063/1.3634065 Influence of gate dielectrics on the performance of single-layered organic transistors and bi-layered organic lightemitting transistors prepared by the neutral cluster beam deposition methodThe neutral cluster beam deposition (NCBD) method has been applied to the production and characterization of ambipolar, heterojunction-based organic light-emitting field-effect transistors (OLEFETs) with a top-contact, multi-digitated, long-channel geometry. Organic thin films of n-type N,N 0 -ditridecylperylene-3,4,9,10-tetracarboxylic diimide and p-type copper phthalocyanine were successively deposited on the hydroxyl-free polymethyl-methacrylate (PMMA)-coated SiO 2 dielectrics using the NCBD method. Characterization of the morphological and structural properties of the organic active layers was performed using atomic force microscopy and X-ray diffraction. Various device parameters such as hole-and electron-carrier mobilities, threshold voltages, and electroluminescence (EL) were derived from the fits of the observed current-voltage and current-voltage-light emission characteristics of OLEFETs. The OLEFETs demonstrated good field-effect characteristics, well-balanced ambipolarity, and substantial EL under ambient conditions. The device performance, which is strongly correlated with the surface morphology and the structural properties of the organic active layers, is discussed along with the operating conduction mechanism. V C 2014 AIP Publishing LLC. [http://dx.

In this study, heterojunction-based organic light-emitting field-effect transistors (OLEFETs) with a top-contact, long-channel geometry were fabricated and comparatively characterized. The neutral cluster beam deposition (NCBD) method was used to successively deposit two layers of p-type pentacene and n-type tris(8-hydroxyquinoline) aluminum (Alq 3 ). For doped OLEFETs, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) was used as a highly fluorescent dye dopant to enhance the light-emission efficiency and change the emission color. OLEFETs revealed fine device characteristics based on deposition of highly crystalline active layers. The combination of the highly fluorescent DCM-doping and asymmetric electrode configuration (Au and Li:Al or LiF/Al) exhibited efficient energy transfer, enhanced electroluminescence (EL) emission. The operating light-emission mechanisms were discussed based on EL photos acquired using a charge-coupled device (CCD) camera.