Wayne Cranton

Growth and dielectric characterization of yttrium oxide thin films deposited on Si by r.f.-magnetron sputtering

Thin films of Y2O3 have been deposited by r.f.-magnetron sputtering onto 100 mm diameter n-type single crystal Si wafers. The growth conditions are discussed including an optical interferometric technique for in-situ thickness monitoring. The dielectric properties of films deposited at 60 °C, 100 °C and 190 °C are measured, with optimum values of the relative dielectric constant and breakdown strength determined as ϵr = 16 and Ebd = 3.85 MVcm-1 respectively. Deposition was uniform with respect to film thickness over 50 cm2 (±5%), and the refractive index of the Y2O3 was determined as n = 1.911

Electrical and structural characteristics of yttrium oxide films deposited by rf-magnetron sputtering on n-Si

Yttrium oxide dielectric films were grown by rf-magnetron sputtering on n-Si(100) substrates and annealed in vacuum at temperatures ranging from 400 to 600 °C. The main aim of this work was the investigation of the interface between the dielectric film and silicon. Both structural (x-ray diffraction and transmission electron microscopy) and electrical characterization were used for this purpose. No structural change was observed on the interfacial native oxide layer after annealing at 600 °C for 1 h. Metal–oxide–semiconductor structures defined by the evaporation of Al electrodes show low leakage currents, moderate dielectric constant (around 14), and high densities of positive charges trapped in the oxide. Hysteresis effects in capacitance–voltage (C–V) curves reduce with the annealing temperature. Another interesting observation is the parallel shift of the C–V curves along the voltage axis with frequency. An insulator trap model is proposed to explain this behavior.

Handbook of Visual Display Technology

This handbook offers a comprehensive description of the science, technology, economic and human interface factors associated with the displays industry. With expert contributions from over 150 international display professionals and academic researchers, it covers all classes of display device and discusses established principles, emergent technologies, and particular areas of application.

Optical encoding by plasmon-based patterning: hard and inorganic materials become photosensitive

The photosensitivity of nanocomposite AlN films with embedded silver nanospheres is reported. It stems from localized surface plasmon resonances (LSPR) whose modulation is photoinduced by laser annealing that induces a combined effect of metallic nanoparticle enlargement and dielectric matrix recrystallization; the photoindunced changes of the refractive index of the matrix result in strong spectral shift of LSPR. We demonstrate the utilization of this process for spectrally selective optical encoding into hard, durable, and chemically inert films.

Intrinsic photoluminescence from low temperature deposited zinc oxide thin films as a function of laser and thermal annealing

An investigation into the modification of low temperature deposited ZnO thin films by different annealing processes has been undertaken using laser, thermal and rapid thermal annealing of 60 nm ZnO films deposited by high-target-utilization sputtering. Single-pulse laser annealing using a KrF excimer laser (λ = 248 nm) over a range of fluences up to 318 mJ cm−2 demonstrates controlled in-depth modification of internal film microstructure and luminescence properties without the film degradation produced by high temperature thermal and RTA processes. Photoluminescence (PL) properties show that the ratio of defect related deep level emission (DLE, 450–750 nm, 2.76–1.65 eV) to excitonic near band-edge emission (NBE at 381 nm, 3.26 eV) is directly correlated to processing parameters. Thermal and rapid thermal processing results in the evolution of a strong visible orange/red DLE PL (with peaks at 590 nm, 2.10 eV and 670 nm, 1.85 eV) dominated by defects related to excess oxygen. At higher temperatures, the appearance of a green/yellow emission (530 nm, 2.34 eV) indicates a transition of the dominant radiative transfer mechanism. In contrast, laser processing removes defect related DLE and produces films with intense NBE luminescence, correlated to the observed formation of large grains (25–40 nm).

Characterisation of the BaTiO3/p-Si interface and applications

Barium titanate (BaTiO3), because of its high dielectric constant ( er), has proven to be a very promising candidate for use as dielectric layer in ac thin film electroluminescent (ACTFEL) devices and for use in thin film hybrid and integrated circuits. In the present work, BaTiO3 films were deposited on p-Si (100) substrates by rf-magnetron sputtering at a base temperature of 200°C. The electronic properties of the BaTiO3/p-Si interface were examined by means of admittance spectroscopy on metal–insulator–semiconductor (MIS) devices fabricated by thermal evaporation of Al. The density of interface states (Dit) was calculated by both the capacitive and the conductive response of the traps; values of the order of 1012 eV−1 cm−2 were obtained for the Dit and values of 10−5 s were calculated for the relevant time constants of the traps. These values, together with the dielectric constant of the films ranging between 40 and 60, show that the deposited films were suitable for use as cladding insulators in ACTFEL devices.

High efficiency ZnS:Mn ac thin film electroluminescent device structure

A method for improving the luminous efficiency of a ZnS:Mn ac thin film electroluminescent device by modifying the structure to include thin, 100 A, barrier layers of a Y2O3 is presented, with experimental comparisons of devices showing a fourfold increase in efficiency. The results are discussed in terms of electron tunneling and field redistribution as the mechanisms responsible for the enhancement of efficiency.

The effects of KrF pulsed laser and thermal annealing on the crystallinity and surface morphology of radiofrequency magnetron sputtered ZnS:Mn thin films deposited on Si

Thin films of ZnS:Mn (800 nm) have been deposited by rf magnetron sputtering onto 100 mm diam n-type single-crystal (100) Si wafers. Specifically for use as active layers in thin film electroluminescent devices, the films need a postdeposition annealing treatment to enhance their luminescent properties. Inherent to the later process step are structural modifications of the phosphor layer which form the basis of this study. Both pulsed laser and thermal postannealing techniques have been investigated. Reported are the induced crystalline and surface morphology modifications via x-ray diffraction and atomic force microscopy analysis. As-grown and thermally treated films were cubic in nature and no significant grain growth or reorientation occurred while heating up to 700 °C. Pulsed (∼ 20 ns duration) KrF laser treated samples were annealed at power densities from 10.76 to 24.27 MW/cm2 under 10.34 bar of argon pressure. Beam quality and diagnostics were emphasized during laser irradiation with particular attention brought to energy and pulse duration measurements. It has been demonstrated that at the power densities used, a gradual phase transition from cubic to hexagonal is occurring while the average crystallite size remains constant. Surface analysis highlights concomitance between the phase transition and the smoothening of the irradiated surface. A one dimensional thermal model of the pulsed laser annealing process shows that a surface temperature for crystalline ZnS equating to the transition temperature should be reached at 17 MW/cm2, significantly below the numerically evaluated melting threshold of 30.5 MW/cm2. Combining experimental and theoretical results, it is concluded that the phase transition occurs in the solid state.Thin films of ZnS:Mn (800 nm) have been deposited by rf magnetron sputtering onto 100 mm diam n-type single-crystal (100) Si wafers. Specifically for use as active layers in thin film electroluminescent devices, the films need a postdeposition annealing treatment to enhance their luminescent properties. Inherent to the later process step are structural modifications of the phosphor layer which form the basis of this study. Both pulsed laser and thermal postannealing techniques have been investigated. Reported are the induced crystalline and surface morphology modifications via x-ray diffraction and atomic force microscopy analysis. As-grown and thermally treated films were cubic in nature and no significant grain growth or reorientation occurred while heating up to 700 °C. Pulsed (∼ 20 ns duration) KrF laser treated samples were annealed at power densities from 10.76 to 24.27 MW/cm2 under 10.34 bar of argon pressure. Beam quality and diagnostics were emphasized during laser irradiation with particular att...

Simulating visual impairments using the Unreal Engine 3 game engine

This paper describes the development of a visual impairment simulator created using the Unreal Engine 3 game engine. A game mod based upon the Unreal Tournament 3 game was produced which harnessed the game engines post process chain functionality to reproduce the appearance of a series of visual impairments. This virtual reality environment was then tested by 3 different user groups: A set of professionally qualified opticians, a visually impaired consultant who runs impairment awareness workshops, and a group of students. The paper concludes that the Unreal Engine 3 was a suitable platform for developing an effective and accurate simulation of visual impairments. It also demonstrates that, following exposure to the virtual environment, users of the simulation reported and demonstrated a greater awareness of the nature of visual impairments. Furthermore they reported improved understanding of the difficulties visually impaired people face.

Pulsed KrF laser annealing of ZnS : Mn laterally emitting thin film electroluminescent displays

Abstract Pulsed KrF (248-nm) laser annealing was investigated as a post-deposition process for RF sputtered ZnS:Mn phosphor layers used in laterally emitting thin film electroluminescent (LETFEL) displays. LETFEL devices consist of a phosphor layer sandwiched between two insulating thin films (Y 2 O 3 ), grown onto silicon substrates patterned with micro-mirrors (SiO 2 ). The micro mirror structure permits surface viewing by reflecting laterally emitted light due to internal waveguiding effects. Laser irradiation of the uncoated phosphor layer was performed using KrF excimer 248-nm laser pulses of 20 ns under an argon overpressure of 10.34 bars to limit laser ablation. The influence of the laser irradiation fluence on the LETFEL performance was investigated from 0.3 to 1.5 J/cm 2 . In this paper, we have reported the brightness-voltage characteristics of laser annealed, non-annealed and thermally annealed devices at 500°C for ∼1 h. It is shown that the onset for light emission (threshold voltage) decreases with laser annealing. Using this novel method of annealing, the brightness of LETFEL devices is observed to increase with increasing laser fluence.