• Research

    Pulsed Laser deposition of oxide films

    Pulsed Laser Deposition (PLD) is an excellent technique to deposit oxide films, in particular, transparent conductive oxide (TCO) films. The third harmonic (355 nm) of a Nd:YAG laser is used to deposit some TCOs, such as indium-tin-oxide (ITO), ZnO:Al (AZO), or fluorine-doped tin oxide (FTO) on various substrates, also at low temperature. TCO films are electrically characterized in order to evaluate the carrier density and mobility. Characteristics of TCO films are expected to be strongly dependent on deposition parameters, such as substrate temperature, laser fluence, and oxygen pressure. We can optimize the process in order to find the best deposition conditions. (more info)
  • ZnO p-doping

    We investigate on the possibility to obtain p-type doped ZnO by pulsed laser deposition. ZnO target are syntherised with the desired amount of dopants, by a 25 MPa hydraulic press and a 1000°C oven. Element such as Li, Cu, and P are tested as possible p-type dopants. Furthermore, we try to dope ZnO films deposited on InP by out-diffusion of the phosphorus from the InP substrate. (more info)
  • Memristors

    Memristors are nonlinear, bias-dependent resistors, which can be used as memory elements. They are characterized for exhibiting resistive switching between a high-resistance state (HRS) and a low-resistance state (LRS) and have been recently considered as one of the most promising candidates for next-generation nonvolatile memory devices. Resistive switching behaviour is observed in microscale memristors based on laser-ablated ZnO and VO2. In particular ZnO has recently attracted much attention as oxide material for resistive switching application, due to its abundance in nature, which means low cost, and compatibility with CMOS technology, in terms of process integration and device scalability down to nanometric sizes. Our results show that devices up to 300 x 300 mm² exhibit a memristive behaviour regardless of device size, and 100 x 100 mm² ZnO-based memristor have the best resistance off/on ratio. (more info)
  • White LEDs by frequency conversion of organic dyes

    High efficiency cool white light emitting diodes (LEDs) are obtained by generation of frequency down-conversion from a GaN/InGaN blue LED. Using photoluminescence of a perylene-based polymer dye we achieve a good substitute for conventional inorganic colour conversion. Record values of 9.37 lm of luminous flux and 118.23 lm/W of optical efficacy are achieved (with 20 mA of driving current). (more info)
  • Organic thin-film transistors

    Fabricated devices consist of FET structures (metal/anodic oxide/polymer/source-drain metallization) prepared on vacuum-deposited oxides (Ta2O5, Nb2O5). The OTFTs are electrically characterised in order to evaluate the device performance, but also to investigate some physical properties of the semiconductive polymer, such as resistivity and carrier mobility. Drain currents vs. drain voltages are measured as a function of gate voltage by means of a self-made parameter analyzer based on a Keithley 6487 source-picoammeter. (more info)
  • Fabrication of dielectric mirrors and filters

    Dielectric distributed Bragg reflectors (DBR) for nitride-based vertical cavity surface-emitting lasers (VCSEL) are deposited by CO2 laser-assisted thermal evaporation. As known, the refractive index step is larger in dielectric than in nitride DBR, meaning that a less number of layers is necessary. We can design and fabricate DBR for each wavelength. As an example, we fabricated a DBR centered on 420 nm and reflectivity of at least 99.5% with only 6 pairs of ZnS/MgF2 layers. (more info)

University of Palermo  -  Department of Energy, Information engineering and Mathematical models (DEIM)
viale delle Scienze, Building 9  -  I-90128  Palermo (Italy)