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10 Nov 2008

Volume 93, Issue 19, Articles (19xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 192501 (2008); http://dx.doi.org/10.1063/1.3013857 (3 pages)

O. Hellwig, A. Moser, E. Dobisz, Z. Z. Bandic, H. Yang, D. S. Kercher, J. D. Risner-Jamtgaard, D. Yaney, and E. E. Fullerton
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Efficient infrared electroabsorption with 1 V applied voltage swing using intersubband transitions

P. Holmström, P. Jänes, U. Ekenberg, and L. Thylén

Appl. Phys. Lett. 93, 191101 (2008); http://dx.doi.org/10.1063/1.3013360 (3 pages) | Cited 2 times

Online Publication Date: 10 November 2008

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We have demonstrated efficient intersubband electroabsorption in InGaAs/InAlGaAs/InAlAs step quantum wells grown by metal-organic vapor-phase epitaxy. An absorption modulation of 6 dB (Δα = 2300 cm−1) at λ ∼ 5.7 μm due to Stark shift of the intersubband resonance was achieved at a low applied voltage swing of ±0.5 V in a multipass waveguide structure. The interface intermixing was estimated by comparing experimental and theoretical Stark shifts. It is predicted that the present material in a strongly confining surface plasmon waveguide can yield an electroabsorption modulator with a peak-to-peak voltage of Vpp = 0.9 V and modulation speed of f3dB ≈ 130 GHz.
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78.20.Jq Electro-optical effects
78.67.De Quantum wells
78.30.Fs III-V and II-VI semiconductors

Azimuthal dependent reflection anisotropy spectroscopy of Ag(110) near the plasmon resonance energy

T. Farrell, P. Harrison, C. I. Smith, D. S. Martin, and P. Weightman

Appl. Phys. Lett. 93, 191102 (2008); http://dx.doi.org/10.1063/1.3021016 (3 pages) | Cited 5 times

Online Publication Date: 10 November 2008

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The reflection anisotropy (RA) of Ag(110) has been investigated near 3.9 eV as a function of azimuthal angle θ using a photoelastically modulated spectrometer. At 3.9 eV the RA signal was small and varied as sin 4θ. At photon energies away from 3.9 eV the signal increased and varied as cos 2θ. Jones vector modeling of the system showed that in addition to the commonly observed cos 2θ dependence, which disappears when the reflection is isotropic, there is a sin 4θ dependence that occurs when the underlying dielectric function is anisotropic; in cubic materials this term is small but for other materials it may be very large.
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78.68.+m Optical properties of surfaces
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Air-voids embedded high efficiency InGaN-light emitting diode

Eun-Hyun Park, Jin Jang, Shalini Gupta, Ian Ferguson, Cheol-Hoi Kim, Soo-Kun Jeon, and Joong-Seo Park

Appl. Phys. Lett. 93, 191103 (2008); http://dx.doi.org/10.1063/1.2998596 (3 pages) | Cited 21 times

Online Publication Date: 11 November 2008

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To improve the light extraction efficiency of InGaN-light emitting diode (LED), inverted hexagonal cone shaped air voids with {10–11} GaN crystal planes were formed between a patterned sapphire substrate and GaN epitaxial layer using a H3PO4-based hot chemical etching method. The air-voids embedded LED showed 12% and 210% higher optical power than a patterned substrate LED and a flat substrate LED, respectively. A ray tracing simulation revealed that the light extraction through the top face of the air-voids embedded LED was dramatically increased due to a strong light reflection and redirection by the air voids.
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85.60.Jb Light-emitting devices

Fiber lasers generating radially and azimuthally polarized light

Moti Fridman, Galina Machavariani, Nir Davidson, and Asher A. Friesem

Appl. Phys. Lett. 93, 191104 (2008); http://dx.doi.org/10.1063/1.3023072 (2 pages) | Cited 24 times

Online Publication Date: 11 November 2008

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A simple, robust, and efficient method to produce either radially or azimuthally polarized output beam from a fiber laser is presented. Experimental results reveal that polarization purity of 90% or better can be obtained.
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42.55.Wd Fiber lasers
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Broadband Raman amplification in silicon

Daniel R. Solli, Prakash Koonath, and Bahram Jalali

Appl. Phys. Lett. 93, 191105 (2008); http://dx.doi.org/10.1063/1.3005408 (3 pages) | Cited 6 times

Online Publication Date: 12 November 2008

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Raman gain is a useful nonlinear phenomenon that has made optically pumped silicon lasers and amplifiers a reality. Unfortunately, the bandwidth of Raman gain in silicon is normally rather limited, owing to the narrow Raman linewidths typical of crystalline materials. Here, we report Raman amplification in silicon with a spectrum that is modified by the simultaneous occurrence of self-phase-modulation. This combined nonlinear action produces a broad Raman gain spectrum from a narrowband pump source.
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42.55.Ye Raman lasers
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Ultrastable in reflection photonic crystal fiber modal interferometer for accurate refractive index sensing

Rajan Jha, Joel Villatoro, and Gonçal Badenes

Appl. Phys. Lett. 93, 191106 (2008); http://dx.doi.org/10.1063/1.3025576 (3 pages) | Cited 21 times

Online Publication Date: 12 November 2008

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A compact in reflection modal interferometer consisting of a stub of large-mode area photonic crystal fiber (PCF) spliced to standard fiber is presented. In the splice, the voids of the PCF are fully collapsed allowing so coupling and recombining PCF core and cladding modes. The interferometer is highly stable over time and can be used for different applications. The measuring of refractive index in the 1.33–1.45 range with high sensitivity is demonstrated. Sensing applications based on refractive index changes are also feasible.
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42.81.Pa Sensors, gyros
07.60.Ly Interferometers
07.60.Hv Refractometers and reflectometers
42.81.Wg Other fiber-optical devices

The effect of injector barrier thickness and doping level on current transport and optical transition width in a λ ∼ 8.0 μm quantum cascade structure

Scott S. Howard, Daniel P. Howard, Kale Franz, Anthony Hoffman, Deborah L. Sivco, and Claire F. Gmachl

Appl. Phys. Lett. 93, 191107 (2008); http://dx.doi.org/10.1063/1.3028013 (3 pages) | Cited 1 time

Online Publication Date: 12 November 2008

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We experimentally study the optical transition width and current transport properties of a set of λ ∼ 8.0 μm quantum cascade (QC) structures with varying injector barrier thickness and doping level. For this high-performance QC laser structure, a 50% reduction in doping level and a 33% reduction in injection barrier thickness yield five times stronger luminescence, 20% smaller optical transition linewidth, and improved current-voltage characteristics. These results demonstrate how high-performance QC laser structures can be engineered to produce narrow gain spectra at and above room temperature.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
61.72.U- Doping and impurity implantation

Variation of the feedback sensitivity in a 1.55 μm InAs/InP quantum-dash Fabry–Perot semiconductor laser

F. Grillot, N. A. Naderi, M. Pochet, C.-Y. Lin, and L. F. Lester

Appl. Phys. Lett. 93, 191108 (2008); http://dx.doi.org/10.1063/1.2998397 (3 pages) | Cited 10 times

Online Publication Date: 13 November 2008

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Dynamic feedback properties of a 1.55 μm InAs/InP quantum dash laser are reported. The ground state linewidth enhancement factor (αH-factor) is found to be enhanced from ∼ 1 to ∼ 14 as the bias current is increased beyond the threshold value. As a consequence of the variation in the αH-factor, the feedback sensitivity of the quantum dash semiconductor laser is dramatically affected over the entire range of operational currents. The onset of its critical feedback regime, which is incompatible with data transmission, is shown to exhibit a variation of approximately 20 dB for the quantum dash device.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Liquid phase direct laser printing of polymers for chemical sensing applications

Christos Boutopoulos, Vasiliki Tsouti, Dimitrios Goustouridis, Stavros Chatzandroulis, and Ioanna Zergioti

Appl. Phys. Lett. 93, 191109 (2008); http://dx.doi.org/10.1063/1.3025596 (3 pages) | Cited 16 times

Online Publication Date: 13 November 2008

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This letter demonstrates the direct laser printing of polymers on capacitive micromechanical arrays for the realization of a chemical sensor. Each sensor of a single chip array is composed of a thin Si membrane covered by a chemically sensitive polymer layer by means of a direct laser printing technique. We present the high spatial resolution deposition of three different sensitive polymer materials by the liquid phase laser induced forward transfer process. We also show that the optimum sensitivity of the sensors can be achieved by varying the percentage of the coverage of the sensors’ membranes with the polymer.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

A dual-resonant terahertz metamaterial based on single-particle electric-field-coupled resonators

Yu Yuan, Christopher Bingham, Talmage Tyler, Sabarni Palit, Thomas H. Hand, Willie J. Padilla, Nan Marie Jokerst, and Steven A. Cummer

Appl. Phys. Lett. 93, 191110 (2008); http://dx.doi.org/10.1063/1.3026171 (3 pages) | Cited 19 times

Online Publication Date: 13 November 2008

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We report the design, fabrication, and measurement of a terahertz metamaterial composed of single geometry electric field coupled resonators that has two closely spaced electric resonances near 1.0 and 1.5 THz. Due to the mutual coupling between the different resonances in the particle, the lower frequency resonance of this metamaterial is stronger than that in a metamaterial composed of identically sized single-resonant particles, leading to a larger insertion loss and broader bandwidth. This feature provides more flexibility in metamaterial design and application in the terahertz regime.
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42.70.-a Optical materials
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.-e Optical elements, devices, and systems

Intensity detection of terahertz quantum cascade laser radiation using electro-optic sampling

R. Rungsawang, O. Marshall, J. R. Freeman, H. E. Beere, S. Malik, J. Alton, S. Barbieri, and D. A. Ritchie

Appl. Phys. Lett. 93, 191111 (2008); http://dx.doi.org/10.1063/1.3027474 (3 pages) | Cited 3 times

Online Publication Date: 13 November 2008

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We demonstrate intensity detection of terahertz radiation from a 2 THz quantum cascade laser with nonsynchronized electro-optic (EO) sampling under crossed polarizers. The detection sensitivity is limited by the residual birefringence of the EO detection crystal. With 100 fs fiber laser pulses and a CdTe EO crystal, terahertz radiation with power less than 100 μW was detected. A femtosecond gating pulse provides an ultrashort detection response that is potentially very useful for analyzing temporal performance of short pulsed radiation or observing fast phenomena probed by terahertz pulses.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.55.Wd Fiber lasers

Photoresponses in polycrystalline silicon phototransistors incorporating germanium quantum dots in the gate dielectrics

S. S. Tseng, I. H. Chen, and P. W. Li

Appl. Phys. Lett. 93, 191112 (2008); http://dx.doi.org/10.1063/1.3028023 (3 pages) | Cited 5 times

Online Publication Date: 13 November 2008

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Polycrystalline silicon (poly-Si) thin-film transistors (TFTs) incorporating germanium (Ge) quantum dots (QDs) in the gate oxide were fabricated as efficient blue to near ultraviolet phototransistors for light detection and amplification. Under 405–450 nm light illumination, Ge QDs poly-Si TFTs exhibit not only strong photoresponses in the drive current but also much improved subthreshold characteristics than that measured in darkness. This originates from the fact that only photoexcited holes within Ge QDs are injected into the active channel via vertical electric field and contribute excess mobile carriers for photocurrent but without the associated photogenerated electron induced junction barrier lowering.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Tv Field effect devices

Design principles for particle plasmon enhanced solar cells

K. R. Catchpole and A. Polman

Appl. Phys. Lett. 93, 191113 (2008); http://dx.doi.org/10.1063/1.3021072 (3 pages) | Cited 174 times

Online Publication Date: 14 November 2008

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We develop fundamental design principles for increasing the efficiency of solar cells using light trapping by scattering from metal nanoparticles. We show that cylindrical and hemispherical particles lead to much higher path length enhancements than spherical particles, due to enhanced near-field coupling, and that the path length enhancement for an electric point dipole is even higher than the Lambertian value. Silver particles give much higher path length enhancements than gold particles. The scattering cross section of the particles is very sensitive to the thickness of a spacer layer at the substrate, which provides additional tunability in the design of particle arrays.
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84.60.Jt Photoelectric conversion
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Direct characterization of focusing light by negative refraction in a photonic crystal flat lens

Jie Tian, Min Yan, Min Qiu, Carl G. Ribbing, Ya-Zhao Liu, Dao-Zhong Zhang, and Zhi-Yuan Li

Appl. Phys. Lett. 93, 191114 (2008); http://dx.doi.org/10.1063/1.3027069 (3 pages) | Cited 4 times

Online Publication Date: 14 November 2008

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We report experimental measurements of the field distribution of the light spot focused by a two-dimensional photonic crystal flat lens at wavelengths 1.51–1.58 μm. The photonic crystal slab is fabricated on a silicon-on-insulator substrate by focused-ion-beam direct milling. We confirm the light focusing by the photonic crystal slab through direct observation of the light spot entering into free space at the end facet of the slab lens. The beam profiles as the function of lateral position are measured and the minimal full width half maximum of the beam at 1.2 μm (0.77λ) is obtained.
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42.79.-e Optical elements, devices, and systems
42.86.+b Optical workshop techniques
42.70.Qs Photonic bandgap materials

Observation of injection locking in an optomechanical rf oscillator

Mani Hossein-Zadeh and Kerry J. Vahala

Appl. Phys. Lett. 93, 191115 (2008); http://dx.doi.org/10.1063/1.3028024 (3 pages) | Cited 5 times

Online Publication Date: 14 November 2008

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Injection locking of a radiation-pressure optomechanical oscillator is demonstrated through external modulation of the optical pump power near the optomechanical oscillation frequency. It is shown that the frequency and phase of a microtoroidal optomechanical oscillator can be locked to those of an electronic oscillator (or any other signal) that can modulate the optical input power and whose frequency is within the lock range.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
07.10.Cm Micromechanical devices and systems

Quantum-dot light-emitting diodes utilizing CdSe/ZnS nanocrystals embedded in TiO2 thin film

Seung-Hee Kang, Ch. Kiran Kumar, Zonghoon Lee, Kyung-Hyun Kim, Chul Huh, and Eui-Tae Kim

Appl. Phys. Lett. 93, 191116 (2008); http://dx.doi.org/10.1063/1.3028070 (3 pages) | Cited 14 times

Online Publication Date: 14 November 2008

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Quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated on Si wafers by embedding core-shell CdSe/ZnS nanocrystals in TiO2 thin films via plasma-enhanced metallorganic chemical vapor deposition. The n-TiO2/QDs/p-Si LED devices show typical p-n diode current-voltage and efficient electroluminescence characteristics, which are critically affected by the removal of QD surface ligands. The TiO2/QDs/Si system we presented can offer promising Si-based optoelectronic and electronic device applications utilizing numerous nanocrystals synthesized by colloidal solution chemistry.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.30.Kk Junction diodes

Transformable broad-band transparency and amplification in negative-index films

Alexander K. Popov and Sergey A. Myslivets

Appl. Phys. Lett. 93, 191117 (2008); http://dx.doi.org/10.1063/1.3028651 (3 pages) | Cited 14 times

Online Publication Date: 14 November 2008

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The possibility to produce laser-induced optical transparency of a metamaterial slab through the entire negative-index frequency domain is shown above a certain control laser field intensity threshold.
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78.66.-w Optical properties of specific thin films
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Wc Optical coatings
42.70.-a Optical materials

Low threshold lasing of GaN-based vertical cavity surface emitting lasers with an asymmetric coupled quantum well active region

Jiang-Yong Zhang, Li-E Cai, Bao-Ping Zhang, Shui-Qing Li, Feng Lin, Jing-Zhi Shang, Du-Xiang Wang, Ke-Chuang Lin, Jin-Zhong Yu, and Qi-Ming Wang

Appl. Phys. Lett. 93, 191118 (2008); http://dx.doi.org/10.1063/1.3030876 (3 pages) | Cited 2 times

Online Publication Date: 14 November 2008

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We have fabricated and characterized GaN-based vertical cavity surface emitting lasers (VCSELs) with a unique active region structure, in which three sets of InGaN asymmetric coupled quantum wells are placed in a half-wavelength (0.5λ) length. Lasing action was achieved under optical pumping at room temperature with a threshold pumping energy density of about 6.5 mJ/cm2. The laser emitted a blue light at 449.5 nm with a narrow linewidth below 0.1 nm and had a high spontaneous emission factor of about 3.0×10−2. The results indicate that this active region structure is useful in reducing the process difficulties and improving the threshold characteristics of GaN-based VCSELs.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Improved wall plug efficiency of a 1.9 THz quantum cascade laser by an automated design approach

Joshua R. Freeman, Owen Marshall, Harvey E. Beere, and David A. Ritchie

Appl. Phys. Lett. 93, 191119 (2008); http://dx.doi.org/10.1063/1.3030881 (3 pages) | Cited 1 time

Online Publication Date: 14 November 2008

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We demonstrate an improvement in the wall plug efficiency in a bound-to-continuum quantum cascade laser operating below 2 THz. This was achieved by targeting one perceived weakness in a previous design, extraction from the lower laser state. This targeted improvement was made possible by employing an automated search algorithm to select a design giving rise to specified electronic states. The resulting laser design represents the highest wall plug efficiency below 2 THz and the lowest frequency devices to operate in the high-power single plasmon waveguide. The device displays a wall plug efficiency of 1.2% per facet, double the reference design.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
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Ion trajectories in plasma ion implantation of slender cylindrical bores using a small inner end source

Xiubo Tian, Chunzhi Gong, Yongxian Huang, Haifu Jiang, Shiqin Yang, Ricky K. Y. Fu, and Paul K. Chu

Appl. Phys. Lett. 93, 191501 (2008); http://dx.doi.org/10.1063/1.2988192 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2008

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Plasma immersion ion implantation (PIII) into slender cylindrical bores with higher efficiency is described in this letter. The use of an inner end plasma source excited by a radio-frequency hollow cathode is investigated theoretically and experimentally. The end source that is covered by a small grounded shielding electrode to ensure steady discharge enables continuous delivery of the required plasmas, and the potential difference in the tube increases the ion impact energy. Particle-in-cell simulation demonstrates that the ion trajectories are complex due to the special electric field configuration that is composed of three regions characterized by ion acceleration, no electric field, and ion deceleration. The end source structure with the open shielding electrode is insufficient to achieve high ion energy, although it is effective in maintaining a steady discharge in the source. Hence, a shielding electrode with a protruding electrode structure is required to conduct high energy PIII; a cylindrical bore with an inner diameter of 20 mm is successfully implanted.
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52.77.Dq Plasma-based ion implantation and deposition
52.80.Pi High-frequency and RF discharges
52.50.Dg Plasma sources
52.65.Rr Particle-in-cell method

Low power density multihole cathode very-high-frequency plasma for mixed phase Si:H thin films

C. Jariwala, A. Chainani, R. Eguchi, M. Matsunami, S. Shin, S. Bhatt, V. Dalal, and P. I. John

Appl. Phys. Lett. 93, 191502 (2008); http://dx.doi.org/10.1063/1.3023066 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2008

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A low power density very-high-frequency (VHF) (55 MHz) H2 plasma in a capacitively coupled multihole-cathode (MHC) geometry is studied using Langmuir probe measurements. Radial profiles show a higher ion density (Ni) and lower electron temperature (Te) compared to a MHC 13.56 MHz H2 plasma. The Ni dependence on power indicates an Ohmic plasma, while Te is essentially constant. The MHC-VHF plasma is used to investigate mixed phase microcrystalline+amorphous (μc+a-) Si:H thin films at a substrate temperature of 60 °C. High-resolution photoemission suggests two types of Si, with concentrations in agreement with atomic force microscopy images showing ∼ 510±40 nm crystallites embedded in a-Si:H matrix. The results show that the low power density MHC-VHF plasma is a high-Ni Ohmic collisional plasma, suitable for low temperature deposition of μc+a-Si:H thin films.
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52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors
52.25.-b Plasma properties

Effects of 2 mass % Si admixture in a laser-produced Fe plasma

Josef Krása, Leoš Láska, Karel Rohlena, Andriy Velyhan, Antonella Lorusso, Vincenzo Nassisi, Agata Czarnecka, Piotr Parys, Leszek Ryć, and Jerzy Wolowski

Appl. Phys. Lett. 93, 191503 (2008); http://dx.doi.org/10.1063/1.3021362 (3 pages) | Cited 4 times

Online Publication Date: 11 November 2008

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Emission of multiply charged ions and soft x-rays from the plasmas produced by laser pulses focused on (111) surface of Fe and Fe−2 mass % Si single crystals is investigated for wavelengths of 1064 and 248 nm and intensities up to ≈ 1×1010 W/cm2. It is demonstrated that the Si admixture in the Fe plasma results in a higher emission of Feq+ ions (1 ≤ q ≤ 4) but in a markedly lower x-ray emission. The relation of wavelengths and pulse durations of laser beams used is figured in the fluence dependence of the ion emission.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Ultrafast laser ablation of metals with a pair of collinear laser pulses

S. Amoruso, R. Bruzzese, X. Wang, and J. Xia

Appl. Phys. Lett. 93, 191504 (2008); http://dx.doi.org/10.1063/1.3026533 (3 pages) | Cited 2 times

Online Publication Date: 12 November 2008

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We investigated the process of ultrafast laser ablation of metallic targets induced by a pair of identical laser pulses, with either p or s polarizations, temporally delayed from ≈ 1 ps to a few nanoseconds. We used fast ion probe diagnostics to characterize the ion plume at the moderate laser intensity ( ≈ 1012 W/cm2) typically employed in ultrafast laser deposition and material processing. We observed a consistent time-correlated enhancement of the ion yield and velocity, which lends itself to an interesting and useful method for manipulating ablation plasma characteristics. The mechanisms producing this feature are also discussed.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.38.Mf Laser ablation
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties

Microwave-excited atmospheric-pressure plasma jets using a microstrip line

Jaeho Kim, Makoto Katsurai, Dongmin Kim, and Hyroyuki Ohsaki

Appl. Phys. Lett. 93, 191505 (2008); http://dx.doi.org/10.1063/1.3025841 (3 pages) | Cited 13 times

Online Publication Date: 13 November 2008

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We report a 2.45 GHz microwave-excited atmospheric-pressure plasma jet (MW-APPJ) device using a microstrip line for materials processing. A three-dimensional simulation based on the finite difference time domain method revealed that the configuration of the MW-APPJ device results in a strong concentration of electric fields at the gas nozzle. Argon plasmas were generated at the nozzle and were blown into ambient air with the maximum length of 5 mm at a microwave power of 40 W. The rotational temperatures of molecular nitrogen in the downstream of the plasma jets, measured by optical emission spectroscopy, were 1720 to 900 K for gas flow rates from 0.5 to 3.5 l/min, indicating that the jets were nonthermal plasmas. This MW-APPJ device will provide a large-area APPJ for materials processing depending on the configuration of the nozzle array and microstrip lines.
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52.75.-d Plasma devices
52.65.-y Plasma simulation

Characteristics of Al2O3 gate dielectrics partially fluorinated by a low energy fluorine beam

Sung Woo Kim, Byoung Jae Park, Se Koo Kang, Bo Hyun Kong, Hyung Koun Cho, Geun Young Yeom, Sungho Heo, and Hyunsang Hwang

Appl. Phys. Lett. 93, 191506 (2008); http://dx.doi.org/10.1063/1.2975183 (3 pages) | Cited 4 times

Online Publication Date: 14 November 2008

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The partial fluorination of Al2O3 gate dielectrics was examined by exposing an oxide-nitride-aluminum oxide (ONA) stack to a low energy fluorine beam, and its effect on the properties of the ONA was investigated. Exposing ONA to about 10 eV fluorine beam resulted in a 5-nm-thick AlOxFy layer on the ONA by replacing some Al–O to Al–F. The electrical properties such as leakage current and memory window characteristics were improved after fluorination of the ONA, possibly due to the improved charge trapping characteristics through the formation of an AlOxFy layer on the Al2O3 without changing the blocking layer thickness.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
84.30.Sk Pulse and digital circuits
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