共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Wadeasa S. L. Beegum S. Raja O. Nur M. Willander 《Applied Physics A: Materials Science & Processing》2009,95(3):807-812
We report a demonstration of heterojunction light emitting diode (LED) based on a hybrid n-ZnO-nanorod/p-polymer layered structure.
The ZnO was grown using the aqueous chemical growth (ACG) on top of the polymer(s) which were deposited on glass. The current–voltage
(I–V) behavior of the heterojunctions showed good rectifying diode characteristics. Room-temperature electroluminescence (EL)
spectra of the LEDs provided a broad emission band over a wide LED color range (430–650 nm), in which both zinc and oxygen
vacancy peaks are clearly detected. We present here luminescent devices based on the use of ZnO-nanorods in combination with
two different blended and multi-layered p-type polymers. Electroluminescence of the first batch of devices showed that white
bluish strong emission for the presently used polymers is clearly observed. We obtained a turn-on voltage of 3 V and break-down
voltage equal to −6 V for PVK-TFB blended device. The corresponding values for the NPD-PFO multilayer device were 4 V and
−14 V, respectively. The rectification factors were equal to 3 and 10 for the two devices, respectively. The films and devices
processed were characterized by scanning electron microscopy (SEM), DEKTAK 3ST Surface Profile, Semiconductor Parameter Analyzer,
photoluminescence (PL), and electroluminescence (EL). 相似文献
2.
Enhanced luminance of organic light-emitting diodes with metal nanoparticle electron injection layer
Deang Liu Michael Fina Li Ren Samuel S. Mao 《Applied Physics A: Materials Science & Processing》2009,96(2):353-356
Improvement of the performance of organic light-emitting diodes (OLEDs) was achieved by implementing Magnesium-Nickel nanoparticles
at the cathode–organic interface using pulsed laser deposition technique. The small geometry of Mg-Ni nanoparticles acts to
enhance the localized electric field around them, thus increasing electron injection through tunneling, from the cathode to
the organic layer. Improved current and luminance characteristics were demonstrated for both small molecule and polymer-based
OLEDs when the nanoparticle layer was incorporated. 相似文献
3.
Recombination zone and efficiency in bipolar single layer light-emitting devices: a numerical study 总被引:1,自引:0,他引:1
Ying-Quan Peng Qing-Sen Yang Hong-Wei Xing Xun-Shuan Li Jian-Ting Yuan Chao-Zhu Ma Run-Sheng Wang 《Applied Physics A: Materials Science & Processing》2008,93(2):559-564
The efficiency of organic light-emitting devices (OLEDs) is closely related to the position and width of recombination zone
(RCZ) in the emission layer. Based on the drift–diffusion theory of carrier motion in semiconductors, we developed a numerical
model for the position and width of the RCZ in bipolar single layer OLEDs. The calculation results show that for a given operation
voltage, the position and width of the RCZ are determined by the mobility difference of electrons and holes, and the energy
barrier at the two contacts. When the anode and cathode contact are both ohmic, then RCZ will be near the electrode, from
which the low-mobility carriers are injected, and the smaller the mobility difference, the wider the RCZ, and the width of
RCZ will be maximal when the mobility of holes and electrons are equal. When the anode contact is Schottky, while the cathode
contact is ohmic, then the position and width of RCZ will be determined by both the mobility difference and hole–injection
energy barrier. When μ
p<μ
n, the RCZ will be at the anode side. When μ
p>μ
n, then RCZ will move away from the anode and become wider, with the increase of the hole injection barrier. For a given hole–injection
barrier and mobility of holes and electrons, the position and width of RCZ change with the applied voltage. 相似文献
4.
Heng Pan Nipun Misra Seung H. Ko Costas P. Grigoropoulos Nate Miller Eugene E. Haller Oscar Dubon 《Applied Physics A: Materials Science & Processing》2009,94(1):111-115
Nanoparticle solutions are considered promising for realizing low cost printable high performance flexible electronics. In
this letter, excimer laser annealing (ELA) was employed to induce melting of solution-deposited ZnO nanoparticles and form
electrically conductive porous films. The properties of the films were characterized by scanning electron microscopy, high-resolution
transmission electron microscopy, DC conductance, and photoluminescence measurements. Thin-film field-effect transistors have
been fabricated by ELA without the use of conventional vacuum or any high temperature thermal annealing processes. The transistors
show n-type accumulation mode behavior with mobility greater than 0.1 cm2/V s and current on/off ratios of more than 104. Optimization and control of the laser processing parameters minimized thermal impact on the substrate. This technique can
be beneficial in the fabrication of metal oxide based electronics on heat sensitive flexible plastic substrates using low-cost,
large-area solution processing combined with direct printing techniques. 相似文献
5.
M. Salaün M. Audier M. Duneau F. Delyon 《Applied Physics A: Materials Science & Processing》2008,93(1):105-110
In 2000, Campbell et al. (Nature 404:53, 2000) have shown that three-dimensional periodic nanostructures can be obtained from UV laser interference irradiation of photoresist
for 6 nanosecond single pulse. We have developed a similar experiment for photolytic gas phase decomposition and for photopatternable
organic–inorganic hybrid resins.
Different steps in results, presently reported, were first to determine the characteristics of both the 3D interference pattern
and interferometer to be associated to a CVD reactor and second to verify the mechanical stability of the set up confirmed
with the structuration of a siloxane based methacrylic resins by UV polymerization and finally to grow periodic nanostructures
by photolytic gas phase decomposition of chromyl chloride. The experimental results obtained so far indicate that, depending
on the electromagnetic energy density, a vapor phase decomposition of chromyl chloride leads to periodic arrays of either
Cr–O amorphous or Cr2O3 particles on glass and (001)TiO2 substrates at room temperature. 相似文献
6.
S. Besner A. V. Kabashin F. M. Winnik M. Meunier 《Applied Physics A: Materials Science & Processing》2008,93(4):955-959
Inorganic nanoparticles offer novel promising properties for biological sensing and imaging, as well as in therapeutics. However,
these applications are often complicated by the possible toxicity of conventional nanomaterials, arising as a result of inadequate
purification procedures of nanoparticles obtained via synthetic pathways using toxic or non-biocompatible substances. We review
novel femtosecond laser-assisted methods, which enable the preparation of metal nanomaterials in clean, biologically friendly
aqueous environment (“green” synthesis) and thus completely solve the toxicity problem. The proposed methods, including laser
ablation and fragmentation, make possible the production of stable metal colloids of extremely small size (∼2 nm) with a low
coefficient of variation (15–25%). Those nanoparticles exhibit unique surface chemistry and can be used for bio-imaging, cancer
treatment and nanoparticle-enhanced Raman spectroscopy. 相似文献
7.
A. V. Kabashin W. Marine M. Meunier 《Applied Physics A: Materials Science & Processing》2008,93(4):1011-1014
ZnO is known as one of the best materials for the implementation of the random lasing effect, associated with mirror-less
laser emission in a simultaneously amplifying and highly scattering medium. Normally, the fabrication of this medium requires
a rather complicated procedure of deposition and thermal treatment of ZnO-based films on some specific substrates, yielding
wurtzite-orientation ZnO nanocrystals. We demonstrate a rapid synthesis of highly efficient ZnO-based random lasing spots
on a piece of Zn by employing the phenomenon of laser-induced air breakdown. Being ignited near the surface of a Zn target,
plasma of the air breakdown serves as a local reactor to locally transform its properties and thus form a film of well-packed
20–40 nm ZnO nanospheres. Exhibiting extremely high amplification and scattering, this medium is capable of generating the
random lasing effect within the exciton-based photoluminescent band. 相似文献
8.
I. Gallardo K. Hoffmann J. W. Keto 《Applied Physics A: Materials Science & Processing》2009,94(1):65-72
Laser Ablation of Microparticles (LAM) is a process of nanoparticle formation in which microparticles in a flowing aerosol
are continuously ablated by high-power laser pulses. For the first time, we have produced CdSe/ZnS core/shell nanoparticles
using a double ablation apparatus, designed to undergo a two-step LAM process. This process can be inverted to produce ZnS/CdSe
core/shell nanoparticles. The present work focuses on the range around ∼15 nm radius heterostructures and uses high-resolution
transmission electron microscopy (HRTEM) to image core and shells. For smaller particles, core shell structures have been
detected with energy dispersive spectroscopy (EDS) 5 nm spot size beam and fast Fourier transform (FFT) spectra. Differences
in the ablation behavior were measured between the two IIB–VIA type semiconductors. 相似文献
9.
L. Kuna C. Sommer E. Zinterl J. R. Krenn P. Pachler P. Hartmann S. Tasch G. Leising F. P. Wenzl 《Applied Physics A: Materials Science & Processing》2008,93(2):421-427
We report on the micro-fabrication of diffractive optical elements (DOEs) such as 1D, 2D and concentric grating structures
inside the volume of thin silicone films by femtosecond laser direct writing. In addition, we show that such structures can
also be integrated into silicone films that act as encapsulation layers of high power light-emitting diodes. The latter strategy
opens new possibilities to homogenize and to control the light emitted from such devices. 相似文献
10.
N. Fukata S. Matsushita N. Okada J. Chen T. Sekiguchi N. Uchida K. Murakami 《Applied Physics A: Materials Science & Processing》2008,93(3):589-592
Boron (B) or phosphorus (P) doped silicon nanowires (SiNWs) were synthesized by laser ablation. Local vibrational modes of
B were observed in B-doped SiNWs by micro-Raman scattering measurements at room temperature. Fano broadening due to a coupling
between the discrete optical phonon and a continuum of interband hole excitations was also observed in the Si optical phonon
peak for B-doped SiNWs. An electron spin resonance signal due to conduction electrons was observed only for P-doped SiNWs.
These results prove that B and P atoms were doped in substitutional sites of the crystalline Si core of SiNWs during laser
ablation and electrically activated in the sites. 相似文献
11.
A. Kisner M. R. Aguiar A. F. Vaz A. Rojas F. A. Cavarsan J. A. Diniz L. T. Kubota 《Applied Physics A: Materials Science & Processing》2009,94(4):831-836
The ultimate limits of size of the current metal-oxide-semiconductor capacitors can be overcome by preparation of three-dimensional
devices that can vertically be biased using one-dimensional metal nanostructures. Here, we present a general and efficient
approach to the assembly and integration of Au nanocrystals into functional nanoelectrodes of three-dimensional submicrometer-MOS
(0.35 μm2) capacitors, presenting an ultra high capacitance (24±1 pF). The Au nanocrystals were directly produced into a nanoporous
template of anodized aluminum oxide that was evaluated, and the electrical characterization of this device corroborates the
formation of the MOS capacitor. Flat band voltage is independent of sweep voltage range, and negligible hysteresis of capacitance-voltage
curves is observed when sweep voltage ranges from positive to negative and turned again to positive bias. In addition, experimental
results match theoretical analysis and indicate the presence of free surface charges stored in the Au nanostructures. The
demonstrated ability to control the assembling of the nanocrystals and the results of electrical characterization indicate
that the embedded Au nanoelectrodes have a high potential for memory applications based on three-dimensional devices. 相似文献
12.
We performed time-resolved spectroscopy of ZnO quantum dots (QD), and observed exciton energy transfer and dissipation between
QD via an optical near-field interaction. Two different sizes of ZnO QD with resonant energy levels were mixed to test the
energy transfer and dissipation using time-resolved photoluminescence spectroscopy. The estimated energy transfer time was
144 ps. Furthermore, we demonstrated that the ratio of energy transfer between the resonant energy states could be controlled. 相似文献
13.
M. C. Gather R. Jin J. de Mello D. D. C. Bradley K. Meerholz 《Applied physics. B, Lasers and optics》2009,95(1):113-124
We report on electromodulation (EM) spectroscopy studies of phosphorescent multi-layer organic light-emitting diodes (OLEDs)
that are processed from solution. Compared to conventional single-layer OLEDs, they comprise an additional layer of a crosslinkable,
oxetane-functionalized triphenylamine-dimer (XTPD) that is inserted between the PEDOT:PSS anode and the emissive layer. Devices
with optimized stack architecture feature reduced operating voltages and reach a current efficiency approaching 40 cd/A—twice
as much as the corresponding single-layer device. Using EM measurements, we quantify the electric field in the XTPD layer
and the emissive layer of such a multi-layer OLED and also measure the average electric field in a single-layer reference
device. By comparing the dependence of the internal field on the applied voltage for devices with and without the XTPD layer,
we find that in the device containing the XTPD layer there is an increased accumulation of electrons at the anode side of
the emissive layer. This accumulation enhances the recombination probability and supports the injection of holes into the
emissive layer which explains the observed efficiency improvement and reduction in operating voltage compared to conventional
single-layer OLEDs. 相似文献
14.
Z. Liu D. J. Styers-Barnett A. A. Puretzky C. M. Rouleau D. Yuan I. N. Ivanov K. Xiao J. Liu D. B. Geohegan 《Applied Physics A: Materials Science & Processing》2008,93(4):987-993
The nucleation and rapid growth of single-wall carbon nanotubes (SWNTs) were explored by pulsed-laser assisted chemical vapor
deposition (PLA-CVD). A special high-power, Nd:YAG laser system with tunable pulse width (>0.5 ms) was implemented to rapidly
heat (>3×104°C/s) metal catalyst-covered substrates to different growth temperatures for very brief (sub-second) and controlled time periods
as measured by in situ optical pyrometry. Utilizing growth directly on transmission electron microscopy grids, exclusively
SWNTs were found to grow under rapid heating conditions, with a minimum nucleation time of >0.1 s. By measuring the length
of nanotubes grown by single laser pulses, extremely fast growth rates (up to 100 microns/s) were found to result from the
rapid heating and cooling induced by the laser treatment. Subsequent laser pulses were found not to incrementally continue
the growth of these nanotubes, but instead activate previously inactive catalyst nanoparticles to grow new nanotubes. Localized
growth of nanotubes with variable density was demonstrated through this process and was applied for the reliable direct-write
synthesis of SWNTs onto pre-patterned, catalyst-covered metal electrodes for the synthesis of SWNT field-effect transistors. 相似文献
15.
The growth mechanism of scales of crystalline SiC nanowires (SiC-NWs) obtained by directly evaporating solid carbon on silicon
wafer with/without ZnS powders at varying temperatures is being discussed. More aligned SiC-NWs of small size and good crystalline
structure were formed when ZnS was used. Random SiC-NWs of big size and poor crystalline structure were obtained at conditions
free of ZnS. Furthermore, the improved crystalline structure and increased diameter of SiC-NWs were observed when the higher
temperature was employed. 相似文献
16.
J. J. Camacho M. Santos L. Díaz J. M. L. Poyato 《Applied Physics A: Materials Science & Processing》2009,94(2):373-380
We have used ferrocene and paraffin wax as novel precursor and solvent for the growth of iron oxide nanoparticles. The proposed
method of growth has several advantages over existing methods of growth using iron pentacarbonyl a precursor. Highly crystalline
and monodispersed particles are obtained which assemble in two- and three-dimensional hexagonal closed packed superlattices.
Growth kinetics has been studied by varying concentration of the precursor and time of growth. A phenomenological model has
been proposed to explain the growth kinetics. 相似文献
17.
Y. Liu T. P. Chen M. Yang Z. H. Cen X. B. Chen Y. B. Li S. Fung 《Applied Physics A: Materials Science & Processing》2009,95(3):753-756
Electroluminescence (EL) from Al-rich AlN thin films grown on p-type Si substrate by radio frequency (RF) magnetron sputtering
has been observed at room temperature. The light-emitting structure based on the thin films can be driven by an electrical
pulse as short as 10−5 s. No obvious change in the light emission intensity was observed after 106 pulse cycles. It has been found that the light emission intensity increases with the Al concentration. It is shown that the
phenomenon is due to the enhancement of the percolative conduction via the Al nanocrystals distributed in the AlN matrix as
a result of the increase in Al concentration. 相似文献
18.
White light-emitting diodes (WLEDs) were fabricated by combining InGaN-based blue light-emitting diodes (LEDs) with highly
luminescent Tb3Al5O12:Ce3+ (TAG:Ce), Y3Al5O12:Ce3+ (YAG:Ce), and Sr3SiO5:Eu2+ (SS:Eu). The TAG:Ce-based WLED showed a color rendering index (R
a
) of 79 and a luminous efficiency (η
L
) of 34.1 lm/W at 20 mA. The YAG:Ce-based WLED and the SS:Eu-based WLED showed low R
a
values of 75 and 57 but high luminous efficiency values of 38.9 and 41.3 lm/W at 20 mA, respectively. When a mixture of YAG:Ce
and SS:Eu was coated on a blue LED and the resultant WLED operated at 20 mA, the WLED showed a highly bright white light similar
to daylight (η
L
=40.9 lm/W, color temperature T
c
=5,716 K, and R
a
=76). Moreover, the WLED showed stable color coordinates against a considerable variation of applied current. 相似文献
19.
ZnO nanoparticles, nanowires, and nanowalls were synthesized rapidly on Si via thermal decomposition of zinc acetate by a
modified chemical vapor deposition at a low substrate temperature of 200–250°C for the first time. The diameters of the synthesized
nanoparticles and nanowires are around 100 and 30 nm, respectively, and the thickness of nanowalls is around 20 nm. High-resolution
transmission electron microscopy shows that the nanowires as well as nanowalls are single-crystalline, and the nanoparticles
are highly-textured poly-crystalline structures. Room-temperature photoluminescence spectra of the nanostructures show strong
ultraviolet emissions centered at 368–383 nm and weak violet emissions at around 425 nm, indicating good crystal quality.
The study provides a simple and efficient route to synthesize ZnO diverse nanostructures at low temperature. 相似文献
20.
A methodology is proposed for studying the suitability of the light emitting diode (LED) as the optical sensor of a miniature
multispectral radiometer. The optoelectronic properties of three commercially available LEDs of three different wavebands
were standardized by measuring the open-circuit voltage and short-circuit currents at different light intensities and different
wavelengths of incident radiation. A photoconductive measurement was found to be more useful for obtaining the appropriate
optical response and was suggested as the suitable mode of sensing. The sensor performances were demonstrated for both solar
photometry and surface reflectance measurements. 相似文献