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LASER PLASMA RADIATION STUDIES FOR DROPLET SOURCES IN THE EXTREME ULTRAVIOLET
Title
LASER PLASMA RADIATION STUDIES FOR DROPLET SOURCES IN THE EXTREME ULTRAVIOLET.
Creator
Kamtaprasad, Reuvani, Richardson, Martin, University of Central Florida
Abstract / Description
The advancement of laboratory based Extreme Ultraviolet (EUV) radiation has escalated with the desire to use EUV as a source for semiconductor device printing. Laser plasmas based on a mass-limited target concept, developed within the Laser Plasma Laboratory demonstrate a much needed versatility for satisfying rigorous source requirements. This concept produces minimal debris concerns and allows for the attainment of high repetition rates as well as the accommodation of various laser and...
Show moreThe advancement of laboratory based Extreme Ultraviolet (EUV) radiation has escalated with the desire to use EUV as a source for semiconductor device printing. Laser plasmas based on a mass-limited target concept, developed within the Laser Plasma Laboratory demonstrate a much needed versatility for satisfying rigorous source requirements. This concept produces minimal debris concerns and allows for the attainment of high repetition rates as well as the accommodation of various laser and target configurations. This work demonstrates the generation of EUV radiation by creating laser plasmas from mass-limited targets with indium, tin, and antimony doped droplets. Spectral emission from the laser plasmas is quantified using a flat-field spectrometer. COWAN code oscillator strength predications for each of the dopants were convolved with narrow Gaussian functions creating synthetic spectra for the EUV region between 10 nm - 20 nm. A preliminary comparison was made between the theoretical spectra and experimental results. From this comparison, ion stage transitions for each of the hot dense plasmas generated were assessed.
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Date Issued
2010
Identifier
CFE0003168, ucf:48597
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003168
The Impact of Growth Conditions on Cubic ZnMgO Ultraviolet Sensors
Title
The Impact of Growth Conditions on Cubic ZnMgO Ultraviolet Sensors.
Creator
Boutwell, Ryan, Schoenfeld, Winston, Likamwa, Patrick, Kik, Pieter, Chernyak, Leonid, University of Central Florida
Abstract / Description
Cubic Zn1-xMgxO (c-Zn1-xMgxO) thin films have opened the deep ultraviolet (DUV) spectrum to exploration by oxide optoelectronic devices. These extraordinary films are readily wet-etch-able, have inversion symmetric lattices, and are made of common and safe constituents. They also host a number of new exciting experimental and theoretical challenges. Here, the relation between growth conditions of the c-Zn1-xMgxO film and performance of fabricated ultraviolet (UV) sensors is investigated....
Show moreCubic Zn1-xMgxO (c-Zn1-xMgxO) thin films have opened the deep ultraviolet (DUV) spectrum to exploration by oxide optoelectronic devices. These extraordinary films are readily wet-etch-able, have inversion symmetric lattices, and are made of common and safe constituents. They also host a number of new exciting experimental and theoretical challenges. Here, the relation between growth conditions of the c-Zn1-xMgxO film and performance of fabricated ultraviolet (UV) sensors is investigated. Plasma-Enhanced Molecular Beam Epitaxy was used to grow Zn1-xMgxO thin films and formation conditions were explored by varying the growth temperature, Mg source flux, oxygen flow rate, and radio-frequency (RF) power coupled into the plasma. Material review includes the effect of changing conditions on the film's optical transmission, surface morphology, growth rate, crystalline phase, and stoichiometric composition. Oxygen plasma composition was investigated by spectroscopic analysis under varying oxygen flow rate and applied RF power and is correlated to device performance. Ni/Mg/Au interdigitated metal-semiconductor-metal detectors were formed to explore spectral responsivity and UV-Visible rejection ratio (RR). Zn1-xMgxO films ranged in Mg composition from x = 0.45 - 1.0. Generally, x increased with increasing substrate temperature and Mg source flux, and decreased with increasing oxygen flow rate and RF power. Increasing x was correlated with decreased peak responsivity intensity and increased RR. Device performance was improved by increasing the ratio of O to O+ atoms and minimizing O2+ in the plasma. Peak responsivity as high as 500 A/W was observed in visible-blind phase-segregated Zn1-xMgxO devices, while cubic phase solar-blind devices demonstrated peak responsivity as high as 12.6 mA/W, and RR of three orders of magnitude. Optimal conditions are predicted for the formation of DUV Zn1-xMgxO sensors.
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Date Issued
2013
Identifier
CFE0005087, ucf:50735
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005087
ASSESSING THE VIABILITY OF SOL-GEL NIMGO FILMS FOR SOLAR BLIND DETECTION
Title
ASSESSING THE VIABILITY OF SOL-GEL NIMGO FILMS FOR SOLAR BLIND DETECTION.
Creator
Scheurer, Amber, Schoenfeld, Winston, University of Central Florida
Abstract / Description
Wide bandgap semiconductors have been broadly investigated for their potential to detect and emit high energy ultraviolet (UV) photons. Advancements in deep UV optoelectronic materials would enable the efficient and affordable realization of many medical, industrial and consumer UV optical devices. The traditional growth method, vacuum deposition, is an extremely complicated and expensive process. Sol-gel processing dramatically simplifies facility requirements and can be scaled to industrial...
Show moreWide bandgap semiconductors have been broadly investigated for their potential to detect and emit high energy ultraviolet (UV) photons. Advancements in deep UV optoelectronic materials would enable the efficient and affordable realization of many medical, industrial and consumer UV optical devices. The traditional growth method, vacuum deposition, is an extremely complicated and expensive process. Sol-gel processing dramatically simplifies facility requirements and can be scaled to industrial size. The work presented here involves a novel study of the ternary wide bandgap material Ni1-xMgxO. Films were developed by sol-gel spin coating for investigation of material and electrical properties. This method produced films 200-600 nm thick with surface roughness below 4 nm RMS. Sintered films indicated an improvement from 60% to 90% transmission near the band edge. Additionally, compositional analysis was performed by X-ray Photoelectron Spectroscopy and film defects were characterized by photoluminescence using a continuous wave He-Cd UV laser, revealing the expected oxygen defect at 413nm. This film growth technique has produced thin polycrystalline films with low surface roughness and a high degree of crystalline orientation; crucial characteristics for semiconductor devices. These films have demonstrated the ability to be tuned over the full compositional range from the bandgap of NiO (3.6 eV) to that of MgO (7.8 eV). Optoelectronic devices produced by standard photolithographic techniques are discussed as well as the electrical transport properties of their metal contacts. Based on initial results, these films have demonstrated strong potential as solar blind detectors of UV radiation.
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Date Issued
2011
Identifier
CFH0003800, ucf:44768
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0003800
EXTREME ULTRAVIOLET SPECTRAL STREAK CAMERA
Title
EXTREME ULTRAVIOLET SPECTRAL STREAK CAMERA.
Creator
Szilagyi, John, Richardson, Martin, University of Central Florida
Abstract / Description
The recent development of extreme ultraviolet (EUV) sources has increased the need for diagnostic tools, and has opened up a previously limited portion of the spectrum. With ultrafast laser systems and spectroscopy moving into shorter timescales and wavelengths, the need for nanosecond scale imaging of EUV is increasing. EUVÂÂÂÂ's high absorption has limited the number of imaging options due...
Show moreThe recent development of extreme ultraviolet (EUV) sources has increased the need for diagnostic tools, and has opened up a previously limited portion of the spectrum. With ultrafast laser systems and spectroscopy moving into shorter timescales and wavelengths, the need for nanosecond scale imaging of EUV is increasing. EUVÂÂÂÂ's high absorption has limited the number of imaging options due to the many atomic resonances in this spectrum. Currently EUV is imaged with photodiodes and X-ray CCDs. However photodiodes are limited in that they can only resolve intensity with respect to time and X-ray CCDs are limited to temporal resolution in the microsecond range. This work shows a novel approach to imaging EUV light over a nanosecond time scale, by using an EUV scintillator to convert EUV to visible light imaged by a conventional streak camera. A laser produced plasma, using a mass-limited tin based target, provided EUV light which was imaged by a grazing incidence flat field spectrometer onto a Ce:YAG scintillator. The EUV spectrum (5 nm-20 nm) provided by the spectrometer is filter by a zirconium filter and then converted by the scintillator to visible light (550 nm) which can then be imaged with conventional optics. Visible light was imaged by an electron image tube based streak camera. The streak camera converts the visible light image to an electron image using a photocathode, and sweeps the image across a recording medium. The streak camera also provides amplification and gating of the image by the means of a micro channel plate, within the image tube, to compensate for low EUV intensities. The system provides 42 ns streaked images of light with a temporal resolution of 440 ps at a repetition rate of 1 Hz. Upon calibration the EUV streak camera developed in this work will be used in future EUV development.
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Date Issued
2010
Identifier
CFE0003558, ucf:48905
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003558
DESIGN, FABRICATION, AND TESTING OF HIGH-TRANSPARENCY DEEP ULTRA-VIOLETCONTACTS USING SURFACE PLASMON COUPLING IN SUBWAVELENGTH ALUMINUM MESHES
Title
DESIGN, FABRICATION, AND TESTING OF HIGH-TRANSPARENCY DEEP ULTRA-VIOLETCONTACTS USING SURFACE PLASMON COUPLING IN SUBWAVELENGTH ALUMINUM MESHES.
Creator
Mazuir, Clarisse, Schoenfeld, Winston, University of Central Florida
Abstract / Description
The present work aims at enhancing the external quantum efficiencies of ultra-violet (UV) sensitive photodetectors (PDs) and light emitting diodes (LEDs)for any light polarization. Deep UV solid state devices are made out of AlGaN or MgZnO and their performances suffer from the high resistivity of their p-doped regions. They require transparent p-contacts; yet the most commonly used transparent contacts have low transmission in the UV: indium tin oxide (ITO) and nickel-gold (Ni/Au 5/5 nms)...
Show moreThe present work aims at enhancing the external quantum efficiencies of ultra-violet (UV) sensitive photodetectors (PDs) and light emitting diodes (LEDs)for any light polarization. Deep UV solid state devices are made out of AlGaN or MgZnO and their performances suffer from the high resistivity of their p-doped regions. They require transparent p-contacts; yet the most commonly used transparent contacts have low transmission in the UV: indium tin oxide (ITO) and nickel-gold (Ni/Au 5/5 nms) transmit less than 50% and 30% respectively at 300 nm. Here we investigate the use of surface plasmons (SPs) to design transparent p-contacts for AlGaN devices in the deep UV region of the spectrum. The appeal of using surface plasmon coupling arose from the local electromagnetic field enhancement near the metal surface as well as the increase in interaction time between the field and semiconductor if placed on top of a semiconductor. An in/out-coupling mechanism is achieved by using a grating consisting of two perpendicularly oriented sets of parallel aluminum lines with periods as low as 250 nm. The incident light is first coupled into SPs at the air/aluminum interface which then re-radiate at the aluminum/AlGaN interface and the photons energy is transferred to SP polaritons (SPPs) and back to photons. High transmission can be achieved not only at normal incidence but for a wider range of incident angles. A finite difference time domain (FDTD) package from R-Soft was used to simulate and design such aluminum gratings with transparency as high as 100% with tunable peak wavelength, bandwidth and angular acceptance. A rigorous coupled wave analysis (RCWA) was developed in Matlab to validate the FDTD results. The high UV transparency meshes were then fabricated using an e-beam assisted lithography lift-off process. Their electrical and optical properties were investigated. The electrical characterization was very encouraging; the sheet resistances of these meshes were lower than those of the conventionally used transparent contacts. The optical transmissions were lower than expected and the causes for the lower measurements have been investigated. The aluminum oxidation, the large metal grain size and the line edge roughness were identified as the main factors of inconsistency and solutions are proposed to improve these shortcomings. The effect of aluminum oxidation was calculated and the passivation of aluminum with SiO2 was evaluated as a solution. A cold deposition of aluminum reduced the aluminum grain size from 60 nm to 20 nm and the roughness from 5 nm to 0.5 nm. Furthermore, replacing the conventional lift-off process by a dry back-etch process led to much smoother metal line edges and much high optical transparency. The optical measurements were consistent with the simulations. Therefore, reduced roughness and smooth metal line edges were found to be especially critical considerations for deep UV application of the meshes.
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Date Issued
2011
Identifier
CFE0003645, ucf:48893
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003645