scholarly journals Demonstration of using HF-etchant mixed into CO2 to lift-off thin-film GaAs layers by supercritical fluid technology

2021 ◽  
Author(s):  
David Jui-Yang Feng ◽  
Heng Kuo ◽  
Cheng-Fu Yang
Keyword(s):  
Sacrificial Layer ◽  
Volume Ratio ◽  
Adhesive Layer ◽  
Etching Time ◽  
Free Standing ◽  
Pressure System ◽  
Fixed Temperature ◽  
Pdms Stamp ◽  
Etching Method ◽  
Lift Off

The epitaxial lift-off (ELO) process based on selectively etching a thin sacrificial AlAs layer from GaAs substrate was performed using high-concentrated aqueous hydrofluoric (HF) etchant. However, because of using the wet etching method, the traditional ELO process has many drawbacks and limitations. Supercritical fluids (SCFs) naturally have the characteristics of low viscosity, high diffusivity, and zero surface tension. Therefore, the development of a gas-phase-like dry etching method based on mixing HF into CO2 and operating the mixture of HF/CO2 in SCFs condition as etchant is hereby proposed to overcome those bottlenecks existing in traditional wet ELO processes. However, there are no available experimental results for etching AlAs layers by HF in SCFs yet. Therefore, a HF-compatible corrosion-resistant high-pressure system was designed and built up to perform the idea. The capabilities of etching sample in supercritical CO2 (scCO2) had been systemically investigated under various pressures (2000–3000 psi) and temperatures (40–60[Formula: see text]C). Besides, the etching performances separately conducted by using aqueous-HF and anhydrous HF/Pyridine as the source etchant and mixing with scCO2 at a fixed temperature, pressure and etching time were also examined and compared under different equivalent HF concentrations. An evaluation of using acetone as the co-solvent mixed with HF/scCO2 mixture for enhancing the etch rate in different volume ratio of HF/co-solvent was further investigated and discussed. With this system, we demonstrate releasing a size of [Formula: see text] (width × length) and 3 [Formula: see text]m-thick free-standing GaAs sheet from a 150 nm AlAs sacrificial layer by the etching sample in HF/scCO2 mixture. The released GaAs sheet was also successfully transferred to a flexible PET substrate by using a PDMS stamp and an adhesive layer of NOA61.

scholarly journals Mass Transfer of Microscale Light-Emitting Diodes to Unusual Substrates by Spontaneously Formed Vertical Tethers During Chemical Lift-Off

2019 ◽  
Vol 9 (20) ◽  
pp. 4243 ◽  
Author(s):  
Ja-Yeon Kim ◽  
Yoo-Hyun Cho ◽  
Hyun-Sun Park ◽  
Jae-Hyun Ryou ◽  
Min-Ki Kwon
Keyword(s):  
Mass Transfer ◽  
Sacrificial Layer ◽  
Adhesive Layer ◽  
Practical Method ◽  
Electrical Characteristics ◽  
Light Emitting ◽  
Full Color ◽  
Simplified Method ◽  
Lift Off ◽  
Led Arrays

A much simplified method for transferring Gallium nitride (GaN) light emitting didoes (LEDs) to an unusual substrate, such as glass, Si, polyethylene terephthalate, or polyurethane, was demonstrated with spontaneously formed vertical tethers during chemical lift-off (CLO), without requiring a sacrificial layer or extra process steps. The LED arrays resided on a stamp that was coated with an adhesive layer. After the layer with the LEDs was transferred to the new substrates, the stamp was removed by acetone to complete the preparation. Over 3 × 3 cm2 LED arrays transferred to various substrates without any damage and misorientation. We also found that the optical and electrical characteristics improved after transfer due to decease in built-in stress. This simple and practical method is expected to greatly facilitate the development of transferrable full color GaN microLEDs on various substrates with either greatly reduced or no damage.

Fabrication of Free-Standing Polymer Membranes via Imprint Lithography and Selective Immobilization of Lipid Vesicles at Micropores in the Membrane

2007 ◽  
Author(s):  
Anish Roychowdhury ◽  
Junseo Choi ◽  
Alum Yi ◽  
Feng Xu ◽  
Sunggook Park
Keyword(s):  
Pore Diameter ◽  
Sacrificial Layer ◽  
Membrane Surface ◽  
Polymer Membranes ◽  
Uv Curing ◽  
Lipid Vesicles ◽  
Imprint Lithography ◽  
Free Standing ◽  
Fundamental Study ◽  
Lift Off

This study presents fabrication of free-standing, perforated membranes in polymer with the pore diameter down to 500 nm via novel imprint lithography and use of the membrane to selectively immobilize lipid vesicles at the micropores in the membrane. For the fabrication, a combination of imprint lithography and a sacrificial layer technique was employed in order to get a clean, fully released, and mechanically stable membrane with perforated pores. Si molds with microscale pillar structures fabricated via photolithography were used to define patterns in SU-8 resist layer which was spin-coated on lift-off resist (LOR) used as a sacrificial layer. This was followed by a UV curing process to achieve enough mechanical strength in the SU-8 layer to be fee-standing. Release of the SU-8 layer from the LOR sacrificial layer by lift-off results in the free-standing, perforated membranes with pore diameter down to sub-micrometer range. Prior to the application of lipid vesicles, the SU-8 membrane surface was treated with poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) which prevents non-specific adsorption of the lipid vesicles on the membrane surface. As a result, lipid vesicles were found to selectively adsorb at the pore sites in the membrane, as observed with an evanescence fluorescence microscope. This result indicates that the perforated polymer membranes with micro- and nanoscale pores have potential as a platform for fundamental study of biological systems.

Free standing GaN nano membrane by laser lift-off method

2012 ◽  
Vol 1432 ◽  
Author(s):  
Liang Tang ◽  
Yuefeng Wang ◽  
Gary Cheng ◽  
Michael J. Manfra ◽  
Timothy D. Sands
Keyword(s):  
Defect Density ◽  
Sacrificial Layer ◽  
Pulsed Laser ◽  
Large Area ◽  
Free Standing ◽  
Sapphire Substrates ◽  
Device Applications ◽  
Lift Off ◽  
Gan Film

ABSTRACTIn this work, we present a method able to fabricate thin GaN nanomembranes fit for device applications. Starting from commercial GaN on sapphire substrates, MBE was used to deposit a sacrificial layer, which comprises of a superlattice of InN/InGaN, after which thin a GaN film of hundreds of nanometers thickness was grown on top. Pulsed laser irridiation with photon energy of 2.3eV gives rise to the controlled decomposition of the sacrificial intermediate layer, which can be followed by easy separation of the top GaN membrane from the substrate. This process can be used to manufacture GaN membranes with low defect density and a wider range of thickness. We demonstrated that large area, free-standing GaN membranes, with a thickness from 200nm and up, could be made using this method, and the high crystal quality of the lift-off GaN layers is well preserved in this process.

scholarly journals High-yield fabrication of perpendicularly magnetised synthetic antiferromagnetic nanodiscs

Nano Research ◽  
2021 ◽  
Author(s):  
Emma N. Welbourne ◽  
Tarun Vemulkar ◽  
Russell P. Cowburn
Keyword(s):  
Thin Film ◽  
Magnetic Properties ◽  
Sacrificial Layer ◽  
Nanosphere Lithography ◽  
High Yield ◽  
Perpendicular Anisotropy ◽  
Ion Milling ◽  
Lift Off

AbstractSynthetic antiferromagnetic (SAF) particles with perpendicular anisotropy display a number of desirable characteristics for applications in biological and other fluid environments. We present an efficient and effective method for the patterning of ultrathin Ruderman-Kittel-Kasuya-Yoshida coupled, perpendicularly magnetised SAFs using a combination of nanosphere lithography and ion milling. A Ge sacrificial layer is utilised, which provides a clean and simple lift-off process, as well as maintaining the key magnetic properties that are beneficial to target applications. We demonstrate that the method is capable of producing a particularly high yield of well-defined, thin film based nanoparticles.

scholarly journals Three-dimensional platinum nanoparticle-based bridges for ammonia gas sensing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nishchay A. Isaac ◽  
Johannes Reiprich ◽  
Leslie Schlag ◽  
Pedro H. O. Moreira ◽  
Mostafa Baloochi ◽  
...  
Keyword(s):  
Room Temperature ◽  
Gas Sensing ◽  
Response Times ◽  
High Surface ◽  
Three Dimensional ◽  
Performance Testing ◽  
Volume Ratio ◽  
Platinum Nanoparticle ◽  
Ammonia Gas ◽  
Lift Off

AbstractThis study demonstrates the fabrication of self-aligning three-dimensional (3D) platinum bridges for ammonia gas sensing using gas-phase electrodeposition. This deposition scheme can guide charged nanoparticles to predetermined locations on a surface with sub-micrometer resolution. A shutter-free deposition is possible, preventing the use of additional steps for lift-off and improving material yield. This method uses a spark discharge-based platinum nanoparticle source in combination with sequentially biased surface electrodes and charged photoresist patterns on a glass substrate. In this way, the parallel growth of multiple sensing nodes, in this case 3D self-aligning nanoparticle-based bridges, is accomplished. An array containing 360 locally grown bridges made out of 5 nm platinum nanoparticles is fabricated. The high surface-to-volume ratio of the 3D bridge morphology enables fast response and room temperature operated sensing capabilities. The bridges are preconditioned for ~ 24 h in nitrogen gas before being used for performance testing, ensuring drift-free sensor performance. In this study, platinum bridges are demonstrated to detect ammonia (NH3) with concentrations between 1400 and 100 ppm. The sensing mechanism, response times, cross-sensitivity, selectivity, and sensor stability are discussed. The device showed a sensor response of ~ 4% at 100 ppm NH3 with a 70% response time of 8 min at room temperature.

Electroluminescence and Photoluminescence Properties of Porous Silicon Nanostructures with Optimum Current Density of Photo-Electrochemical Anodisation

2013 ◽  
Vol 667 ◽  
pp. 180-185
Author(s):  
M. Ain Zubaidah ◽  
F.S. Husairi ◽  
S.F.M. Yusop ◽  
Noor Asli Asnida ◽  
Mohamad Rusop ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Volume Ratio ◽  
Boron Doping ◽  
Peak Position ◽  
Silicon Nanostructures ◽  
Etching Time ◽  
Photoluminescence Properties ◽  
Current Densities ◽  
Pl Spectrum ◽  
P Type

P-type silicon wafer ( orientation; boron doping; 0.75 ~ 10 Ω cm-1) was used to prepare samples of porous silicon nanostructures (PSiNs). All samples have been prepared by using photo-electrochemical anodisation. A fixed etching time of 30 minutes and volume ratio of electrolyte, hydrofluoric acid 48% (HF48%) and absolute ethanol (C2H5OH), 1:1 were used for various current densities, J. There were sample A (J=10 mA/cm2), sample B (J=20 mA/cm2), sample C (J=30 mA/cm2), sample D (J=40 mA/cm2) and sample E (J=50 mA/cm2). Photoluminescence (PL) and electroluminescence (EL) spectra were investigated. Maximum peak position of PL spectrum at about ~675 nm, while the maximum EL spectrum at about ~650 nm (which is similar to the PL spectrum).

Effect of current density on the porous silicon preparation as gas sensors**

2021 ◽  
Vol 30 (1) ◽  
pp. 257-264
Author(s):  
Muna H. Kareem ◽  
Adi M. Abdul Hussein ◽  
Haitham Talib Hussein
Keyword(s):  
Porous Silicon ◽  
Gas Sensors ◽  
Current Density ◽  
Room Temperature ◽  
Low Cost ◽  
High Surface ◽  
Volume Ratio ◽  
Etching Time ◽  
Force Microscopy ◽  
Materials Used

Abstract In this study, porous silicon (PSi) was used to manufacture gas sensors for acetone and ethanol. Samples of PSi were successfully prepared by photoelectrochemical etching and applied as an acetone and ethanol gas sensor at room temperature at various current densities J= 12, 24 and 30 mA/cm2 with an etching time of 10 min and hydrofluoric acid concentration of 40%. Well-ordered n-type PSi (100) was carefully studied for its chemical composition, surface structure and bond configuration of the surface via X-ray diffraction, atomic force microscopy, Fourier transform infrared spectroscopy and photoluminescence tests. Results showed that the best sensitivity of PSi was to acetone gas than to ethanol under the same conditions at an etching current density of 30 mA/cm2, reaching about 2.413 at a concentration of 500 parts per million. The PSi layers served as low-cost and high-quality acetone gas sensors. Thus, PSi can be used to replace expensive materials used in gas sensors that function at low temperatures, including room temperature. The material has an exceptionally high surface-to-volume ratio (increasing surface area) and demonstrates ease of fabrication and compatibility with manufacturing processes of silicon microelectronics.

scholarly journals Observation of nonlinear dynamics in an optical levitation system

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Jinyong Ma ◽  
Jiayi Qin ◽  
Geoff T. Campbell ◽  
Giovanni Guccione ◽  
Ruvi Lecamwasam ◽  
...  
Keyword(s):  
Optical Cavity ◽  
Mechanical Quality Factor ◽  
Optical Field ◽  
Free Standing ◽  
Levitation System ◽  
Active Feedback ◽  
Sideband Generation ◽  
Optical Levitation ◽  
Mechanical Oscillators ◽  
Lift Off

Abstract Optical levitation of mechanical oscillators has been suggested as a promising way to decouple the environmental noise and increase the mechanical quality factor. Here, we investigate the dynamics of a free-standing mirror acting as the top reflector of a vertical optical cavity, designed as a testbed for a tripod cavity optical levitation setup. To reach the regime of levitation for a milligram-scale mirror, the optical intensity of the intracavity optical field approaches 3 MW cm−2. We identify three distinct optomechanical effects: excitation of acoustic vibrations, expansion due to photothermal absorption, and partial lift-off of the mirror due to radiation pressure force. These effects are intercoupled via the intracavity optical field and induce complex system dynamics inclusive of high-order sideband generation, optical bistability, parametric amplification, and the optical spring effect. We modify the response of the mirror with active feedback control to improve the overall stability of the system.

scholarly journals Epitaxial lift-off of InGaAs solar cells from InP substrate using a strained AlAs/InAlAs superlattice as a novel sacrificial layer

2019 ◽  
Vol 195 ◽  
pp. 204-212 ◽  
Author(s):  
F. Chancerel ◽  
P. Regreny ◽  
J.L. Leclercq ◽  
S. Brottet ◽  
M. Volatier ◽  
...  
Keyword(s):  
Solar Cells ◽  
Sacrificial Layer ◽  
Inp Substrate ◽  
Lift Off

Pt Schottky contacts on Ga- and N-face surfaces of free-standing GaN

2001 ◽  
Vol 680 ◽  
Author(s):  
U. Karrer ◽  
C.R. Miskys ◽  
O. Ambacher ◽  
M. Stutzmann
Keyword(s):  
Schottky Diodes ◽  
Reverse Current ◽  
Forward Direction ◽  
Hydride Vapor Phase Epitaxy ◽  
Free Standing ◽  
Band Bending ◽  
Barrier Heights ◽  
Consistent Solution ◽  
Lift Off ◽  
Gap States

ABSTRACTThick GaN films, grown by hydride vapor phase epitaxy (HVPE), were separated from their sapphire substrate with a laser-induced lift-off process. After cleaning and polishing, these films offer the most direct way to investigate and compare the influence of crystal polarity on the electronic properties of Ga-face and N-face surfaces, respectively. Different barrier heights for Pt Schottky diodes evaporated onto Ga- and N-face GaN are determined from the dependence of the effective barrier height versus ideality factor by I-V measurements to 1.15 eV and 0.80 eV, respectively. The charge neutrality condition at the surface is modified by the spontaneous polarization due to the polarization induced bound sheet charge. This effect has to be included in the electronegativity concept of metal induced gap states (MIGS) and can also be illustrated by different band bending of the conduction and valence band, inferred from the self-consistent solution of the Schrödinger-Poisson equation. Furthermore, temperature dependent I-V characteristics are compared to simulated behavior of Schottky diodes, exhibiting excellent agreement in forward direction, but showing deviations in the reverse current.

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