Enhanced Electrical Mobilities of Laser Annealed Ga Doped ZnO Thin Films.

In this study, Ga-doped ZnO thin films were prepared, and their potential for transparent conducting oxide applications was assessed. To increase the electrical mobility and reduce the resistance of Ga-doped ZnO thin films, CO2 laser annealing was employed. Recently, the use of transparent conducting oxides (TCOs) have increased, particularly ZnO-based TCOs have been intensively investigated for display applications. To enhance the electrical and optical properties of ZnO thin films, Ga was used as a dopant. First, Ga-doped ZnO thin-film precursors were prepared by the sol-gel method. Subsequently, Ga-doped ZnO thin films were coated on glass substrates by spin coating. Electrical furnace treatment and rapid thermal annealing were employed to obtain and anneal a wurtzite ZnO based structure. The electrical and optical properties of the annealed thin films were optimized by varying the Ga doping concentration. Via Ga doping and optimized laser annealing, the resistivity of the ZnO film could be decreased from 16.32 Ω· cm to 0.45 Ω·cm; notably, the transmittance was similar (85%) in the 380-800 nm range. The transmittance properties of the films are not presented in this paper. Moreover, after an optical CO2 laser annealing process, the conductivity of the films improved by more than 40 times. Furthermore, the electrical properties (mobility, resistivity, and bulk and sheet concentrations) of the CO2-laser-annealed Ga-doped ZnO thin films were optimized.

Possibility of Thermal Energy Recycling Based Light Emitting Diodes Grid System.

Light Emitting Diodes (LED) are highly energy efficient and offer long-life times for display applications. Long life and minimal energy consumption are often the most attractive advantages for electronic devices. Because LEDs are based on compound semiconductors, which explore the direct transition between the conduction and valance band edges, thermal energy loss can be minimized during operation. However, even though these types of LEDs are based on direct transition type semiconductors, thermal energy is still emitted during operation owing to forward conduction and reverse leakage currents. This research proposes capturing this energy loss through thermoelectric module-based energy recycling methods to improve the energy efficiency of LED applications, achieving savings of up to 18%. Additional analysis was performed on high power LED sources resulting in the manufacture of a high-power LED light grid system.

Enhanced Electrical Properties of Platinum Spotted AZO/PET Thin Films Prepared by Sol-Gel Process.

Recently, many researches on Al-doped ZnO (AZO) thin film based transparent conducting oxide (TCO) have been intensively investigated for the electronic and display device applications. In this study, AZO thin films with different thicknesses were deposited on polyethylene terephthalate (PET) substrates by sol-gel spin coating at a relatively low temperature. By optimizing the AZO thickness, maximum figure of merit (FOM) values were investigated and discussed. Commonly, PET substrates are used in the fabrication of flexible display devices. However, because of the low melting temperature of the PET substrate (~200 °C), AZO thin films spin-coated on PET substrates cannot be subjected to crystallization at high temperatures. Therefore, alternative advanced optical annealing method was considered to crystalize the AZO thin films on the PET substrates. In this experiment, optical annealing method will be proposed. To increase electrical conductivity, Platinum (Pt) dots were sprayed on the AZO sample to improve the electric conductivity. The Pt-spotted AZO thin films on flexible PET substrates prepared by sputtering exhibited high electrical conductivities and high optical transmittances. The 0.63 nm-thick Pt/AZO/PET film exhibited a transmittance of 80% in the 380-800 nm range and the 3.78 nm-thick Pt/AZO/PET film exhibited a resistivity of 5.61×10-4 Ώ·m. Notably, the 159 nm-thick Pt/AZO/PET film exhibited an FOM of 156. Moreover, the sheet resistances and transmittances of the prepared AZO/PET films were determined.

Fabrication and Comparison of Self-Organized Ag and Au Nanodots on Ti/MgO(001) Substrates.

We analyze and compare the differences in the dewetting phenomena and crystal structure between Ag(5.0 nm) and Au(5.0 nm) layers deposited on a Ti(1.0 nm) seed layer coated onto a MgO(001) substrate. The samples are deposited at room temperature and annealed at 350-450 °C for 5 h. The surfaces of both Ag/Ti and Au/Ti films exhibit a completely separated island structure, subsequently leading to the formation of a nanodot array after annealing. Based on atomic force microscopy (AFM) analysis, we conclude that the dewetting progression speed of Ag/Ti films is higher than that of Au/Ti films. Based on X-ray diffraction (XRD) results, the Ti thin film acts as a seed layer, assisting the epitaxial growth of fcc-Ag(001) nanodots on the MgO(001) substrate, whereas in the case of Au/Ti, the Au layer grows non-epitaxially on the MgO(001) substrate, which is related to the difference in the surface energies of Ag and Au. Furthermore, the optical absorbance spectra of the self-organized Ag and Au nanodots with the Ti seed layer are obtained in the visible light range and the optical properties of Ag and Au nanodots are compared.

Recycled Thermal Energy from High Power Light Emitting Diode Light Source.

In this research, the recycled electrical energy from wasted thermal energy in high power Light Emitting Diode (LED) system will be investigated. The luminous efficiency of lights has been improved in recent years by employing the high power LED system, therefore energy efficiency was improved compared with that of typical lighting sources. To increase energy efficiency of high power LED system further, wasted thermal energy should be re-considered. Therefore, wasted thermal energy was collected and re-used them as electrical energy. The increased electrical efficiency of high power LED devices was accomplished by considering the recycled heat energy, which is wasted thermal energy from the LED. In this work, increased electrical efficiency will be considered and investigated by employing the high power LED system, which has high thermal loss during the operating time. For this research, well designed thermoelement with heat radiation system was employed to enhance the collecting thermal energy from the LED system, and then convert it as recycled electrical energy.

Near infrared ray annealing effects on the properties of Al-doped ZnO thin films prepared by spin-coating method.

In this research, we will present Al doped ZnO thin films for transparent conducting oxide applications. Aluminum doped zinc oxide (AZO) thin films have been deposited on the glass substrates by sol-gel spin-coating method using zinc acetate dehydrate (Zn(CH3COO)2 2H2O) and aluminum chloride hexahydrate (AlCl3 x 6H2O) as cation sources. In this study, we investigated the effects of near infrared ray (NIR) annealing on the structural, optical and electrical characteristics of the AZO thin films. The experimental results showed that AZO thin films have a hexagonal wurtzite crystal structure and had a good transmittance higher than 85% within the visible wavelength region. It was also found that the additional energy of NIR helps to improve the electrical properties of Al doped ZnO transparent conducting oxides.

High-Temperature Stable Operation of Nanoribbon Field-Effect Transistors.

We experimentally demonstrated that nanoribbon field-effect transistors can be used for stable high-temperature applications. The on-current level of the nanoribbon FETs decreases at elevated temperatures due to the degradation of the electron mobility. We propose two methods of compensating for the variation of the current level with the temperature in the range of 25-150°C, involving the application of a suitable (1) positive or (2) negative substrate bias. These two methods were compared by two-dimensional numerical simulations. Although both approaches show constant on-state current saturation characteristics over the proposed temperature range, the latter shows an improvement in the off-state control of up to five orders of magnitude (-5.2 × 10(-6)).