Nanodiamonds (NDs) have attracted great interest due to their high refractive index and thermal conductivity. The unique properties of NDs, including high thermal conductivity, chemical stability, and tensile strength, make them a promising candidate for enhancing OLED efficiency. NDs were coated either beneath or above the PEDOT:PSS hole injection layer in a green-emitting OLEDs (ITO/ PEDOT:PSS/NPD/CBP:Ir(ppy)3/TPBi/Liq/Al). The best performance is obtained from the device with NDs layer beneath the PEDOT:PSS layer where the current efficiency (CE) is increased by 5.4%, power efficiency (PE) is increased by 17.7% and the external quantum efficiency (EQE) is increased by 4.5% at a luminance of 10000 cd/m2 as compared to a standard device without NDs layer.
Direct laser interference patterning of polyimide (PI) films was performed by using a pulsed 355-nm laser. At laser fluence of 0.4 J/cm2, gratings with spatial periods of 3.8 μm to 344 nm were created. The highest aspect ratio of the grating structure (0.8) was obtained for the 344-nm grating. An all-polymer dye laser was then fabricated by spin-coating a layer of disodium fluorescein (DF)-doped polyvinyl alcohol (PVA) film on bare and patterned PI substrate. Green laser emission was obtained when transversely pumped by a 355-nm laser. The lasing threshold reduced by ∼10 times for the sample with 344-nm grating while the laser intensity was ∼18 times higher. The enhancements are ascribed to the 344-nm grating structures, which act as an efficient distributed feedback resonator and distributed Bragg reflector grating for DF-doped PVA emitting at ∼563 nm, on top of being a passive light-trapping structures.
Al-doped ZnO (AZO) films were deposited on glass and polycarbonate (PC) at room temperature by using pulsed Nd:YAG laser at 355 nm. AZO thin films were obtained for both substrates at laser fluences from 2 to 5 J/cm2 in O2 partial pressure of 2.1 Pa. The effects of laser fluence on the structural, electrical, and optical properties of the films were investigated. The films with lowest resistivity and highest transmittance have been obtained at 2 J/cm2. The resistivities were 2.29×10−3 Ω cm for AZO on glass and 1.49×10−3 Ω cm for AZO on PC. With increasing laser fluence, the deposited films have lower crystallinity, higher resistivity, and smaller optical bandgap.
Several growths of Si nanodots on Si and GaAs substrates were conducted by pulsed laser deposition (PLD) using a KrF
laser of 248nm, 15ns, 12Hz and a Ti-sapphire laser of 800nm, 130fs, 1kHz at 1x10-5mbar vacuum. The laser fluencies on
a Si target were varied from 3 to 32J/cm2 for the nanosecond (ns) PLD growths and 1-2.75J/cm2 for the femtosecond (fs)
PLD. Wide range of nanodots from 20nm to a few micron size droplets were observed from both the ns and fs PLD.
Auger electron spectroscopy of the nanodots was conducted and which indicated that the nanodots were without
contamination.
A technique using a mask consisting of an array of small holes was used to obtain high density nanodots with uniform
size. The array of 100nm diameter holes was created by E-beam lithography. With this technique we have achieved
100nm Si dots with 300nm spacing between them, with few defects. We have observed that laser fluences closer to the
ablation threshold work better for deposition using the EBL mask. In summary, we have demonstrated the growth of
100nm Si nanodots in an array with very few defects using the EBL masking technique.
In this work, nanosecond-pulsed from ultra-violet to infrared lasers: KrF (248 nm, 25 ns) and Nd:YAG (1064
nm, 532 nm, 355 nm, 5 ns) were employed for ablation and deposition of germanium films in background
pressure of <10-6 Torr. Deposition was carried out at room temperature on Si, GaAs, sapphire and glass. The
as-deposited films, characterized by using scanning electron microscopy (SEM) and atomic force microscopy
(AFM), consist of nano to micron-sized droplets on nanostructured film. The dependence of film properties
on laser wavelengths and fluence are discussed.
Effects of O2, N2, Ar and He on the formation of micro- and nanostructured indium tin oxide (ITO) thin films were
investigated in pulsed Nd:YAG laser deposition on glass substrate. For O2 and Ar, ITO resistivity of ≤ 4 × 10-4 Ωcm and
optical transmittance of > 90% were obtained with substrate temperature of 250 °C. For N2 and He, low ITO resisitivity
could be obtained but with poor optical transmittance. SEM images show nano-structured ITO thin films for all gases,
where dense, larger and highly oriented, microcrystalline structures were obtained for deposition in O2 and He, as
revealed from the XRD lines. EDX results indicated the inclusion of Ar and N2 at the expense of reduced tin (Sn)
content. When the ITO films were applied for fabrication of organic light emitting devices (OLED), only those deposited
in Ar and O2 produced comparable performance to single-layer OLED fabricated on the commercial ITO.
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