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15.  ZnO Thin Films & Nanostructures for Emerging Optoelectronic Applications
D.J. Rogers, F. Hosseini Teherani, V.E. Sandana, and M. Razeghi
SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7605, p. 76050K-1-- January 27, 2010 ...[Visit Journal]
ZnO-based thin films and nanostructures grown by PLD for various emerging optoelectronic applications. AZO thin films are currently displacing ITO for many TCO applications due to recent improvements in attainable AZO conductivity combined with processing, cost and toxicity advantages. Advances in the channel mobilities and Id on/off ratios in ZnO-based TTFTs have opened up the potential for use as a replacement for a-Si in AM-OLED and AM-LCD screens. Angular-dependent specular reflection measurements of self-forming, moth-eye-like, nanostructure arrays grown by PLD were seen to have <0.5% reflectivity over the whole visible spectrum for angles of incidence between 10 and 60 degrees. Such nanostructures may be useful for applications such as AR coatings on solar cells. Compliant ZnO layers on mismatched/amorphous substrates were shown to have potential for MOVPE regrowth of GaN. This approach could be used as a means to facilitate lift-off of GaN-based LEDs from insulating sapphire substrates and could allow the growth of InGaN-based solar cells on cheap substrates. The green gap in InGaN-based LEDs was combated by substituting low Ts PLD n-ZnO for MOCVD n-GaN in inverted hybrid heterojunctions. This approach maintained the integrity of the InGaN MQWs and gave LEDs with green emission at just over 510 nm. Hybrid n-ZnO/p-GaN heterojunctions were also seen to have the potential for UV (375 nm) EL, characteristic of ZnO NBE emission. This suggests that there was significant hole injection into the ZnO and that such LEDs could profit from the relatively high exciton binding energy of ZnO. [reprint (PDF)]
 
15.  Comparison of ZnO nanostructures grown using pulsed laser deposition, metal organic chemical vapor deposition, and physical vapor transport
V.E. Sandana, D.J. Rogers, F. Hosseini Teherani, R. McClintock, C. Bayram, M. Razeghi, H-J Drouhin, M.C. Clochard, V. Sallett, G. Garry, and F. Falyouni
Journal of Vacuum Science and Technology B, Vol. 27, No. 3, May/June, p. 1678-1683-- May 29, 2009 ...[Visit Journal]
This article compares the forms and properties of ZnO nanostructures grown on Si (111) and c-plane sapphire (c-Al2O3) substrates using three different growth processes: metal organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), and physical vapor transport (PVT). A very wide range of ZnO nanostructures was observed, including nanorods, nanoneedles, nanocombs, and some novel structures resembelling “bevelled” nanowires. PVT gave the widest family of nanostructures. PLD gave dense regular arrays of nanorods with a preferred orientation perpendicular to the substrate plane on both Si and c-Al2O3 substrates, without the use of a catalyst. X-ray diffraction (XRD) studies confirmed that nanostructures grown by PLD were better crystallized and more highly oriented than those grown by PVT and MOCVD. Samples grown on Si showed relatively poor XRD response but lower wavelength emission and narrower linewidths in PL studies. [reprint (PDF)]
 
15.  Highly Conductive Co-Doped Ga2O3Si-In Grown by MOCVD
Junhee Lee, Honghyuk Kim, Lakshay Gautam and Manijeh Razeghi
Coatings 2021, 11(3), 287; https://doi.org/10.3390/coatings11030287 ...[Visit Journal]
We report a highly conductive gallium oxide doped with both silicon and indium grown on c-plane sapphire substrate by MOCVD. From a superlattice structure of indium oxide and gallium oxide doped with silicon, we obtained a highly conductive material with an electron hall mobility up to 150 cm2/V·s with the carrier concentration near 2 × 1017 cm−3. However, if not doped with silicon, both Ga2O3:In and Ga2O3 are highly resistive. Optical and structural characterization techniques such as X-ray, transmission electron microscope, and photoluminescence, reveal no significant incorporation of indium into the superlattice materials, which suggests the indium plays a role of a surfactant passivating electron trapping defect levels. [reprint (PDF)]
 
15.  The importance of band alignment in VLWIR type-II InAs/GaSb heterodiodes containing the M-structure barrier
D. Hoffman, B.M. Nguyen, E.K. Huang, P.Y. Delaunay, S. Bogdanov, P. Manukar, M. Razeghi, and V. Nathan
SPIE Proceedings, San Jose, CA Volume 7222-15-- January 26, 2009 ...[Visit Journal]
The Type-II InAs/GaSb superlattice photon detector is an attractive alternative to HgCdTe photodiodes and QWIPS. The use of p+ - pi - M - N+ heterodiode allows for greater flexibility in enhancing the device performance. The utilization of the Empirical Tight Binding method gives the band structure of the InAs/GaSb superlattice and the new M- structure (InAs/GaSb/AlSb/GaSb) superlattice allowing for the band alignment between the binary superlattice and the M- superlattice to be determined and see how it affects the optical performance. Then by modifying the doping level of the M- superlattice an optimal level can be determined to achieve high detectivity, by simultaneously improving both photo-response and reducing dark current for devices with cutoffs greater than 14.5 µm. [reprint (PDF)]
 
15.  AlxGa1-xN Materials and Device Technology for Solar Blind Ultraviolet Photodetector Applications
R. McClintock, P. Sandvik, K. Mi, F. Shahedipour, A. Yasan, C. Jelen, P. Kung, and M. Razeghi
SPIE Conference, San Jose, CA, Vol. 4288, pp. 219-- January 22, 2001 ...[Visit Journal]
There has been a growing interest for the development of solar blind ultraviolet (UV) photodetectors for use in a variety of applications, including early missile threat warning, flame monitoring, UV radiation monitoring and chemical/biological reagent detection. The AlxGa1-xN material system has emerged as the most promising approach for such devices. However, the control of the material quality and the device technology are still rather immature. We report here the metalorganic chemical vapor deposition, the n-type and the p-type doping of high quality AlxGa1-xN thin films on sapphire substrates over a wide range of Al concentration. [reprint (PDF)]
 
15.  Fabrication of GaN Nanotubular Material using MOCVD with an Aluminium Oxide Membrane
W.G. Jung, S.H. Jung, P. Kung, and M. Razeghi
Nanotechnology 17-- January 1, 2006 ...[Visit Journal]
GaN nanotubular material is fabricated with an aluminium oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminium oxide membrane with ordered nanoholes is used as a template. Gallium nitride is deposited at the inner wall of the nanoholes in the aluminium oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis conditions in MOCVD are obtained successfully for the gallium nitride nanotubular material in this research. The diameter of the GaN nanotube fabricated is approximately 200–250 nm and the wall thickness is about 40–50 nm. [reprint (PDF)]
 
15.  Electron-spin resonance of the two-dimensional electron gas in Ga0.47In0.53As-InP heterostructures
M. Dobers, J. P. Vieren,, Y. Guldner P. Bove, F. Omnes, and M. Razeghi
Phys. Rev. B 40, 8075(R) – Published 15 October, 1989-- October 15, 1989 ...[Visit Journal]
The microwave-induced change of the magnetoresistivity of Ga0.47In0.53As-InP heterostructures reveals resonant structure which is attributed to electron-spin resonance of the two-dimensional conduction electrons. With microwave frequencies up to 480 GHz and in magnetic fields up to 12 T, we studied the spin splitting of the two lowest Landau levels in different samples. The spin splitting of these Landau levels is a quadratic function of the magnetic field and its extrapolation to zero magnetic field leads to vanishing spin splitting. The g factors depend on the magnetic field B and the Landau level N as follows: g(B,N)=𝑔0-c(N+1/2)B, where 𝑔0 and c are sample-dependent parameters, which are of the order of 𝑔0≊4.1 and c≊0.08 T−1, in the studied heterostructures. [reprint (PDF)]
 
15.  High-power, room-temperature and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ = 4.8 µm
J.S. Yu, S. Slivken, S.R. Darvish, A. Evans, B. Gokden and M. Razeghi
Applied Physics Letters, 87 (4)-- July 25, 2005 ...[Visit Journal]
The authors present high-power continuous-wave (cw) operation of distributed-feedback quantum-cascade lasers. Continuous-wave output powers of 56 mW at 25 °C and 15 mW at 40 °C are obtained. Single-mode emission near 7.8 µm with a side-mode suppression ratio of >=30 dB and a tuning range of 2.83 cm−1 was obtained between 15 and 40 °C. The device exhibits no beam steering with a full width at half maximum of 27.4° at 25 °C in cw mode. [reprint (PDF)]
 
15.  Temperature insensitivity of the Al-free InGaAsP/GaAs lasers for λ = 808 and 908 nm
M. Razeghi, H. Yi, J. Diaz, S. Kim, and M. Erdtmann
SPIE Conference, San Jose, CA; Proceedings 3001-- February 12, 1997 ...[Visit Journal]
n this work, we present our recent achievements for the reliability of the Al-free lasers at high temperatures and high powers. Laser operations up to 30,000 hours were achieved without any degradation in the lasers characteristics from 7 randomly selected InGaAsP/GaAs diodes for λ = 808 nm. The test were performed for lasers without mirror-coating for optical power of 0.5 to 1 W CW at 50 approximately 60 °C. To the best of our knowledge, this is the first direct demonstration of the extremely high reliability of Al-free diodes operations at high powers and temperatures for periods of time much longer than practical need (approximately 3 years). The characteristics during the tests are discussed in detail. [reprint (PDF)]
 
15.  Direct growth of thick AlN layers on nanopatterned Si substrates by cantilever epitaxy
Ilkay Demir, Yoann Robin, Ryan McClintock, Sezai Elagoz, Konstantinos Zekentes, and Manijeh Razeghi
Phys. Status Solidi A, pp. 1–6-- September 30, 2016 ...[Visit Journal]
AlN layers have been grown on 200 nm period of nanopatterned Si (111) substrates by cantilever epitaxy and compared with AlN layers grown by maskless lateral epitaxial overgrowth (LEO) on micropatterned Si (111) substrates. The material quality of 5–10 µm thick AlN grown by LEO is comparable to that of much thinner layers (2 µm) grown by cantilever epitaxy on the nanopatterned substrates. Indeed, the latter exhibited root mean square (RMS) roughness of 0.65 nm and X-ray diffraction full width at half-maximum (FWHM) of 710 arcsec along the (0002) reflection and 930 arcsec along the (10̅15) reflection. The corresponding room temperature photoluminescence spectra was dominated by a sharp band edge peak. Back emission ultra violet light emitting diodes (UV LEDs) were fabricated by flip chip bonding to patterned AlN heat sinks followed by complete Si (111) substrate removal demonstrating a peak pulsed power of ∼0.7 mW at 344 nm peak emission wavelength. The demonstrated UV LEDs were fabricated on a cost effective epitaxial structure grown on the nanopatterned Si substrate with a total thickness of 3.3 µm [reprint (PDF)]
 
15.  InP-based quantum-dot infrared photodetectors with high quantum efficiency and high temperature imaging
S. Tsao, H. Lim, H. Seo, W. Zhang and M. Razeghi
IEEE Sensors Journal, Vol. 8, No. 6, p. 936-941-- June 1, 2008 ...[Visit Journal]
We report a room temperature operating InAs quantum-dot infrared photodetector grown on InP substrate. The self-assembled InAs quantum dots and the device structure were grown by low-pressure metalorganic chemical vapor depositon. The detectivity was 6 x 1010cm·Hz1/2·W-1 at 150 K and a bias of 5 V with a peak detection wavelength around 4.0 micron and a quantum efficiency of 48%. Due to the low dark current and high responsivity, a clear photoresponse has been observed at room temperature. A 320 x 256 middle wavelength infrared focal plane array operating at temperatures up to 200 K was also demonstrated. The focal plane array had 34 mA/W responsivity, 1.1% conversion efficiency, and noise equivalent temperature difference of 344 mK at 120 K operating temperature. [reprint (PDF)]
 
15.  Comparison of the Physical Properties of GaN Thin Films Deposited on (0112) and (0001) Sapphire Substrates
C.J. Sun and M. Razeghi
Applied Physics Letters 63 (7)-- August 16, 1993 ...[Visit Journal]
A direct comparison of the physical properties of GaN thin films is made as a function of the choice of substrate orientations. Gallium nitride single crystals were grown on (0001) and (0112) sapphire substrates by metalorganic chemical vapor deposition. Better crystallinity with fine ridgelike facets is obtained on the (0112) sapphire. Also lower carrier concentration and higher mobilities indicate both lower nitrogen vacancies and less oxygen incorporation on the (0112) sapphire. The results of this study show better physical properties of GaN thin films achieved on (0112) sapphire. [reprint (PDF)]
 
15.  Negative luminescence of InAs/GaSb superlattice photodiodes
F. Fuchs, D. Hoffman, A. Gin, A. Hood, Y. Wei, and M. Razeghi
Phys. Stat. Sol. C 3 (3)-- February 22, 2006 ...[Visit Journal]
The emission behaviour of InAs/GaSb superlattice photodiodes has been studied in the spectral range between 8 µm and 13 μm. With a radiometric calibration of the experimental set-up the internal quantum efficiency has been determined in the temperature range between 80 K and 300 K for both, the negative and positive luminescence. The quantitative analysis of the internal quantum efficiency of the non-equilibrium radiation enables the determination of the Auger coefficient. [reprint (PDF)]
 
15.  Determination of of Band Gap Energy of Al1-xInxN Grown by Metal Organic Chemical Vapor Deposition in the High Al Composition Regime
K.S. Kim, A. Saxler, P. Kung, M. Razeghi, and K.Y. Lim
Applied Physics Letters 71 (6)-- August 11, 1997 ...[Visit Journal]
Ternary AlInN was grown by metal–organic chemical-vapor deposition in the high Al composition regime. The band-gap energy of AlInN ternary was measured by optical absorption spectroscopy at room temperature. The band-gap energy of Al0.92In0.08N is 5.26 eV. The potential application of AlInN as a barrier material for GaN is also discussed. [reprint (PDF)]
 
15.  High quantum efficiency two color type-II InAs/GaSb n-i-p-p-i-n photodiodes
P.Y. Delaunay, B.M. Nguyen, D. Hoffman, A. Hood, E.K. Huang, M. Razeghi, and M.Z. Tidrow
Applied Physics Letters, Vol. 92, No. 11, p. 111112-1-- March 17, 2008 ...[Visit Journal]
A n-i-p-p-i-n photodiode based on type-II InAs/GaSb superlattice was grown on a GaSb substrate. The two channels, with respective 50% of responsivity cutoff wavelengths at 7.7 and 10 µm, presented quantum efficiencies (QEs) of 47% and 39% at 77 K. The devices can be operated as two diodes for simultaneous detection or as a single n-i-p-p-i-n detector for sequential detection. In the latter configuration, the QEs at 5.3 and 8.5 µm were measured as high as 40% and 39% at 77 K. The optical cross-talk between the two channels could be reduced from 0.36 to 0.08 by applying a 50 mV bias. [reprint (PDF)]
 
15.  Monolithic integration of a short‐length GaInAs photoconductor with a GaAs/GaAlAs optical waveguide on a GaAs semi‐insulating substrate
F. Mallecot; J. F. Vinchant; M. Razeghi; D. Vandermoere; J. P. Vilcot; D. Decoster
Appl. Phys. Lett. 53, 2522–2524 (1988)-- December 19, 1988 ...[Visit Journal]
We report the first fabrication of a GaO. 47 Inn. 53 As planar photoconductive detector, associated with a GaAs/GaAIAs rib waveguide grown on a semi-insulating GaAs substrate, which needs a short-length absorbing layer to detect the optical signal. Because of the GaAIAs epilayer, a GalnAs length of about 100 tl1n only is needed to detect 90% of the opticai signal, accordingly to results predicted using a four-layer model with complex refractive indices in each layer. [reprint (PDF)]
 
15.  MOCVD challenge for III-V semiconductor materials for photonic and electronic devices on alternative substrates
M. Razeghi, M. Defour , F. Omnes, P. Maurel , E. Bigan , O. Acher, J. Nagle, F. Brillouet , J.C. Portal
M. Razeghi, M. Defour, F. Omnes, P. Maurel, E. Bigan, O. Acher, J. Nagle, F. Brillouet, J.C. Portal, MOCVD challenge for III-V semiconductor materials for photonic and electronic devices on alternative substrates, Journal of Crystal Growth, Volume 93, Issues 1–4, 1988, Pages 776-781,-- January 1, 1988 ...[Visit Journal]
High quality II[-V semiconductor heterojunctions, quantum wells and superlauices have been grown on lattice matched and alternative substrates such as silicon for photonic and electronic devices, using low pressure metalorganic chemical vapor deposition growth technique. [reprint (PDF)]
 
15.  Optical and crystallographic properties and impurity incorporation of GaxIn1−xAs grown by liquid phase epitaxy, vapor phase epitaxy, and metal organic chemical vapor deposition
K.‐H. Goetz; D. Bimberg; H. Jürgensen; J. Selders; A. V. Solomonov; G. F. Glinskii; M. Razeghi
J. Appl. Phys. 54 (8): 4543–4552 (1983)-- March 29, 1983 ...[Visit Journal]
Optical, crystallographic, and transport properties of nominally undoped n‐type and Zn doped p‐type Gax In1−xAs /InP (0.44 [reprint (PDF)]
 
15.  Use of Sacrificial Zinc Oxide Template Layers for Epitaxial Lift-Off of Yttria-Stabilised Zirconia Thin Films
D. J. Rogers, T. Maroutian, V. E. Sandana, P. Lecoeur, F. H. Teherani, P. Bove and M. Razeghi
Proc. of SPIE 11687, 116872C (2021) ...[Visit Journal]
275 nm-thick Yttria-stabilised zirconia (YSZ) layers were grown on 240 nm-thick epitaxial (0002)-oriented ZnO buffer layers on c-sapphire substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD) studies revealed high quality epitaxial growth with the YSZ having a preferential (111) orientation and a root mean square surface roughness of 1.4 nm over an area of 10 um x 10 um. The YSZ top surface was then temporary bonded to an Apiezon W wax carrier and the sample was immersed in 0.1M HCl so as to preferentially etch/dissolve away the ZnO underlayer and release of the YSZ from the sapphire substrate. XRD revealed only the characteristic (111) peak of YSZ after lift-off and thus confirmed both the dissolution of the ZnO and the preservation of the crystallographic integrity of the YSZ on the wax carrier. Optical and Atomic Force Microscopy revealed some buckling, roughening and cracking of the lifted YSZ, however, which was probably due to tensile epitaxial strain release. [reprint (PDF)]
 
15.  Hybrid green LEDs with n-type ZnO substituted for N-type GaN in an inverted P-N junction
F. Hosseini Teherani; M. Razeghi; D.J. Rogers; Can Bayram; R. McClintock
LEOS Annual Meeting Conference Proceedings, LEOS '09. IEEE, [5343231] (2009) -- October 4, 2009 ...[Visit Journal]
Recently, the GaN and ZnO materials systems have attracted considerable attention because of their use in a broad range of emerging applications including light-emitting diodes (LEDs) and solar cells. GaN and ZnO are similar materials with direct wide bandgaps, wurtzite crystal structure, high thermal stability and comparable thermal expansion coefficients, which makes them well suited for heterojunction fabrication. Two important advantages of GaN over ZnO are the reliable p-type doping and the mature know-how for bandgap engineering. Thus GaN-based LEDs can be made to emit from the deep UV right into the green through alloying with Al and In, respectively. The performance is not identical at all wavelengths, however, and the performance of InGaN-based green LEDs is still relatively poor. [reprint (PDF)]
 
15.  Tl incorporation in InSb and lattice contraction of In1-xTlxSb
J.J. Lee and M. Razeghi
Applied Physics Letters 76 (3)-- January 17, 2000 ...[Visit Journal]
Ternary In1−xTlxSb thin films are grown by low pressure metalorganic chemical vapor deposition in the high In composition region. Infrared photoresponse spectra of the In1−xTlxSb epilayers show a clear shift toward a longer wavelength compared to that of InSb. Tl incorporation is confirmed by Auger electron spectroscopy. In contrast to the theoretical expectation, high resolution x-ray diffraction study reveals that the lattice of the In1−xTlxSb epilayers is contracted by the incorporation of Tl. As more Tl is incorporated, the lattice contraction is observed to increase gradually in the experimental range. A possible origin of this phenomenon is discussed. Our experimental results suggest that the Tl incorporation behavior in In1−xTlxSb differs from that of other group III impurities in III antimonides. [reprint (PDF)]
 
15.  p-doped GaAs/Ga0.51In0.49P quantum well intersub-band photodetectors
J. Hoff, X. He, M. Erdtmann, E. Bigan, M. Razeghi, and G.J. Brown
Journal of Applied Physics 78 (3)-- August 1, 1995 ...[Visit Journal]
Lattice‐matched p-doped GaAs–Ga0.51In0.49P quantum well intersub‐band photodetectors with three different well widths have been grown on GaAs substrates by metal‐organic chemical‐vapor deposition and fabricated into mesa structures. The photoresponse cutoff wavelength varies between 3.5 and 5.5 μm by decreasing the well width from 50 down to 25 Å. Dark current measurements as a function of temperature reveal activation energies for thermionic emission that closely correspond to measured cutoff wavelengths. Experimental results are in reasonable agreement with Kronig–Penney calculations. [reprint (PDF)]
 
15.  Investigation of MgZnO/ZnO heterostructures grown on c-sapphire substrates by pulsed laser deposition
D. J. Rogers ; F. Hosseini Teherani ; P. Bove ; A. Lusson ; M. Razeghi
Proc. SPIE 8626, Oxide-based Materials and Devices IV, 86261X (March 18, 2013)-- March 18, 2013 ...[Visit Journal]
MgZnO thin films were grown on c-sapphire and ZnO-coated c-sapphire substrates by pulsed laser deposition from a ZnMgO target with 4 at% Mg. The MgZnO grown on the ZnO underlayer showed significantly better crystal quality than that grown directly on sapphire. AFM studies revealed a significant deterioration in surface morphology for the MgZnO layers compared with the ZnO underlayer. Optical transmission studies indicated a MgZnO bandgap of 3.61eV (compared with 3.34eV for the ZnO), which corresponds to a Mg content of about 16.1 at%. The MgZnO/ZnO heterojunction showed an anomalously low resistivity, which was more than two orders of magnitude less than the MgZnO layer and an order of magnitude lower than that for the ZnO layer. It was suggested that this may be attributable to the presence of a 2D electron gas at the ZnMgO/ZnO heterointerface. [reprint (PDF)]
 
15.  High-Power (~9 μm) Quantum Cascade Lasers
S. Slivken, Z. Huang, A. Evans, and M. Razeghi
Applied Physics Letters 80 (22)-- June 3, 2002 ...[Visit Journal]
High-power quantum cascade lasers emitting at λ > 9 μm are demonstrated. Accurate control of layer thickness and interfaces is evidenced by x-ray diffraction. Excellent peak power for uncoated lasers, up to 3.5 W per facet for a 25 μm emitter width, is obtained at 300 K for 75 period structures. The threshold current density at 300 K is only 1.4 kA/cm². From 300 to 425 K, the laser exhibits a characteristic temperature, T0, of 167 K. Over 150 mW of average power is measured per facet for a duty cycle of 6%. Simulation of the average power output reveals a thermal resistance of 12 K/W for epilayer-up mounted ridges. [reprint (PDF)]
 
15.  Investigation of the factors influencing nanostructure array growth by PLD towards reproducible wafer-scale growth
Vinod E. Sandana; David. J. Rogers; Ferechteh Hosseini Teherani; Philippe Bove; Manijeh Razeghi
physica status solidi (a) Applications and Materials Science. Volume 211, Issue 2, pages 449–454, (February 2014)-- January 14, 2014 ...[Visit Journal]
The growth of catalyst-free ZnO nanostructure arrays on silicon (111) substrates by pulsed laser deposition was investigated. Without an underlayer, randomly oriented, micron-scale structures were obtained. Introduction of a c-axis oriented ZnO underlayer resulted in denser arrays of vertically oriented nanostructures with either tapering, vertical-walled or broadening forms, depending on background Ar pressure. Nanostructure pitch seemed to be determined by underlayer grain size while nanostructure widths could be narrowed from ∼100–500 to ∼10–50 nm by a 50 °C increase in growth temperature. A dimpled underlayer topography correlated with the moth-eye type arrays while a more granular surface was linked to vertically walled nanocolumns. Between-wafer reproducibility was demonstrated for both moth-eye and vertical nanocolumn arrays. Broadening nanostructures proved difficult to replicate, however. Full 2 inch wafer coverage was obtained by rastering the target with the laser beam. [reprint (PDF)]
 

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