Reactive Ion Etching Method Research Articles

Excellent performance in vertical graphene-C60-graphene heterojunction phototransistors with a tunable bi-directionality

Array integrated all-carbon phototransistor with high photoconductive gain and fast response speed is very attractive for researchers to realize broadband and tunable photo-imaging. Generally, the photoresponse is limited by the low light absorption of carbon materials while the detector array is limited by processing technology. Here, we patterned vertical graphene-C60-graphene heterojunction using photolithograph and deep reactive ion etching method to achieve a sensitive (3.4×105A/W), fast (23 ms) and broadband (405 nm–1550 nm) response. More interestingly, a bi-directional response photocurrent (positive and negative) has been observed, and the response intensity, speed and direction could adjust by changing gate voltage. The different charges transfer mechanism of positive and negative response of fabricated vertical heterojunction device was explored. What’ more, we fabricated 250×250 vertical graphene/C60 film/graphene phototransistors array, which made it possible to realize a large-scale array detection in wide band with all-carbon material.

High-Efficiency Flexible Perovskite Solar Cells Enabled by an Ultrafast Room-Temperature Reactive Ion Etching Process.

Perovskite solar cells (PSCs), which have surprisingly emerged in recent years, are now aiming at commercialization. Rapid, low-temperature, and continuous fabrication processes that can produce high-efficiency PSCs with a reduced fabrication cost and shortened energy payback time are important challenges on the way to commercialization. Herein, we report a reactive ion etching (RIE) method, which is an ultrafast room-temperature technique, to fabricate mesoporous TiO2 (mp-TiO2) as an electron transport layer for high-efficiency PSCs. Replacing the conventional high-temperature annealing process by RIE reduces the total processing time for fabricating 20 PSCs by 40%. Additionally, the RIE-processed mp-TiO2 exhibits enhanced electron extraction, whereupon the optimized RIE-mp-TiO2-based PSC exhibits a power conversion efficiency (PCE) of 19.60% without J-V hysteresis, when the devices were optimized with a TiCl4 surface treatment process. Finally, a flexible PSC employing RIE-mp-TiO2 is demonstrated with 17.29% PCE. Considering that the RIE process has been actively used in the semiconductor industry, including for the fabrication of silicon photovoltaic modules, the process developed in this work could be easily applied toward faster, simpler, and cheaper manufacturing of PSC modules.

Reactive ion etching of Cr-doped Sb2Te3 phase change materials in CHF3/O2 gas

Cr doped Sb2Te3(CST) was considered to be a potential phase-change material mainly due to its fast phase transition and high thermal stability. To manufacture high-integration phase change memory devices, etching technology of CST films is indispensable. Herein we investigated the properties of reactive ion etching of CST thin films in CHF3/O2-based plasma. The etch parameters such as etch rate, selectivity and surface roughness were optimized by varying the CHF3/O2 gas mixture ratio to explore the effect of etching gas on etching quality. We observed that etching of CST films was optimized under the condition of CHF3/O2 gas ratio of 40/10, RF power of 200 W, and chamber pressure of 10 mTorr, i.e. the etch rate was up to 101.8 nm/min, the selectivity to photoresist was 0.78 and the surface was smooth. The etching mechanism and residual products in the etching process were also explored by X-ray photoelectron spectroscopy (XPS). Under the optimized conditions, a highly efficient and low-damage reactive ion etching method for CST materials is obtained.

Enhanced ultrabroadband antireflection properties of ZnTe crystal with sub-wavelength surface structures by maskless reactive ion etching method

Abstract ZnTe as the electro-optic (EO) crystal has been widely used in the THz spectroscopy and imaging system, however, the maximum generation and detection efficiency have yet to be achieved due to surface reflection. In this work, antireflective sub-wavelength structures (SWSs) on ZnTe crystals were fabricated by reactive ion etching (RIE) method. The surface morphology was investigated by tailoring etching time and radio-frequency power. The SWSs with dimensions less than 20 nm spontaneously formed without artificial mask, bringing roughness of 2.07 nm. The infrared and visible-near-infrared transmission spectra demonstrated that the mean transmittance of ZnTe crystals with prepared SWSs was increased 4.4% and 5.8% than as-grown ZnTe crystals, respectively. Simultaneously, the average transmittance in the range of 0.3–2.5 THz was improved ~15.4%. These findings inform an effective way to achieve ultrabroadband (from visible to terahertz) antireflection properties, which is favorable for further enhancing the THz generation and detection efficiency.

Biomimetic Moth-eye Anti-reflective Poly-(methyl methacrylate) Nanostructural Coating

This study reports a simple imprinting method for the fabrication of biomimetic moth-eye antireflective polymethyl methacrylate (PMMA) nanostructures on the surface of the substrate. The antireflection structured silicon was obtained by Reactive Ion Etching (RIE) method. By using the antireflection structured silicon substrate as the imprinting stamp, the biomimetic moth-eye polymer structures showed tapered holes, whose depth and periodicity were around 780 nm and 580 nm, respectively. The reflectance of the resulting PMMA structures was reduced from 10% to less than 1% in the wavelength range from 300 nm to 1600 nm. This simple methodology can be scaled up via self-loading and nanoimprinting, which may have a promising application in optoelectronic devices and solar cells.

Engineering of flexible granular Au nanocap ordered array and its surface enhanced Raman spectroscopy effect

Surface enhanced Raman spectroscopy (SERS) is a new and developing analytical technology in chemical and biological detection. However, traditional hard SERS substrates are struggling to meet the growing demand for flexible devices. In this work, we introduce a simple, cost-effective and large scale preparation route to form a flexible Au nanocap (AuNC) ordered array as SERS substrates via reactive ion etching (RIE) method and then Au deposition. We find RIE is an excellent method for nanoroughening the surface of polystyrene (PS) spheres. Such flexible SERS substrates exhibit high sensitivity and uniformity for detecting organic molecules. The finite-difference time-domain simulation results revealed that a strong electric field coupling effect existed not only in the gap site between the Au nanoparticles (AuNPs), but also in the connection position between the AuNCs and the single AuNP. This study not only offers a novel way for nanoroughening of PS spheres, but also acquires flexible and cheap SERS substrates for quick and sensitive detection of organic molecules.

A Novel Fabrication Process for High Density Silicon Capacitors by using Metal-Assisted Chemical Etching

Abstract In silicon capacitors, it is most important to increase the surface area of the surface forming the capacitor. In conventional silicon capacitors, trenches are generally formed in silicon wafer using reactive ion etching (RIE) method to expand their surface area. However, with this method, the depth of trenches that can be formed was limited. Furthermore, since RIE method processes silicon wafer only one by one, productivity is low. In this paper, Metal-assisted Chemical Etching (MacEtch) is proposed as a novel method of fabricating high-density silicon capacitors to solve the problems. We used gold formed by electroless plating as a catalyst and controlled them by forming conditions. As a result, vertical trenches greater than 100 μm depth and less than 1 μm width could be formed on a silicon wafer. The silicon wafer on which these trenches are formed has a surface area 100 times or more as compared with the case where there is no trench. We formed a dielectric film and electrodes on these trench surfaces. Consequently, we have realized a silicon capacitors with a capacitance density as high as 200 nF / mm2 or more.

A Comparative Study on the Effects of Passivation Methods on the Carrier Lifetime of RIE and MACE Silicon Micropillars

Silicon micropillars have been suggested as one of the techniques for improving the efficiency of devices. Fabrication of micropillars has been done in several ways—Metal Assisted Chemical Etching (MACE) and Reactive Ion Etching (RIE) being the most popular techniques. These techniques include etching through the surface which results in surface damage that affects the carrier lifetime. This paper presents a study that compares the carrier lifetime of micropillars fabricated using RIE and MACE methods. It also looks at increasing carrier lifetime by surface treatment using three main approaches: surface passivation by depositing Al2O3, surface passivation by depositing SiO2/SiN, and surface passivation by etching using KOH and Hydrofluoric Nitric Acetic (HNA) solution. It was concluded that passivating with SiO2 and SiN results in the highest carrier lifetime on the MACE and RIE pillars.

Fabrication of Porous Silicon using Photolithography and Reactive Ion Etching (RIE)

Phenomena of electrical and optical properties in porous silicon (PSi) remain interested. In this study, we focus on fabrication of PSi on N-type Si(100) surface using photolithography and reactive ion etching (RIE) methods with variations of etching times for10, 20, 30, and 40 min. SEM analysis demonstrated similar Psi in shape and size. Based on the profilometer and the four-point probe (FPP) measurement, the pore depth and the resistivity of Psi increase with the increasing etching time. The pores can be consideredas a defect on the silicon surface which inhibits electron diffusion so that the resistivity will increase.

Fabrication of Nanopatterns on Silicon Surface by Combining AFM-Based Scratching and RIE Methods

This study presents an atomic force microscope (AFM)-based scratching combined with reactive ion etching (RIE) method to fabricate nanopatterns on the silicon surface. All AFM-based scratching processes are performed on the polymethylmethacrylate (PMMA) film to create features in order to protect the AFM tip from wearing and enlarge its life time. Two types of resist films are selected for the RIE process. One is only PMMA thin-film resist, and the other one contains two-layer thin-film resist which are PMMA and aluminum thin films. The nanopatterns on the silicon after etching using RIE with these two types of resist film are compared. Results show that when using PMMA film, the width of the nanopattern on silicon is larger than on the PMMA film, and the material pile-ups formed during the scratching process cannot be considered as a resist. On the contrary, the aluminum thin films can improve the quality of the transfer. It indicates that the thin-film resist with bilayers can guarantee the transfer accuracy of the features, which can expand the application of the AFM tip-based scratching technique.

A strong saddle-shaped surface-to-volume ratio effect on the Young's modulus of silicon nanotubes

Single crystalline silicon nanotubes along the [001] direction with different outer diameters and wall thicknesses have been successfully prepared via a high-fidelity nanofabrication process by combining electron-beam lithography and reactive-ion etching methods. A higher specific surface-to-volume ratio compared with other solid one-dimensional nanomaterials has been achieved. In situ compression results revealed a strong saddle-shaped surface-to-volume ratio effect on the Young's modulus, and the Young's modulus increases to a peak value at a surface-to-volume ratio of ∼0.04 nm−1 and then decreases at a higher surface-to-volume ratio. A single core with a double shell model is proposed to interpret this unique saddle-shaped surface-to-volume ratio effect, which may play a guiding role in designing the nanoscale objects for device applications.

Nanoporous metallic thin films prepared by dry processes

Nanoporous Pt and Au thin films were prepared by dry etching methods and compared to those prepared by conventional wet etching (dealloying). While reactive ion etching (RIE) and deep RIE methods did not yield nanoporous structures with high roughness factors (<5), gentle XeF2 dry etching yielded thin metallic nanoporous films (∼200 nm) with high enough roughness factors (∼40). The nanoporous films were as good as those prepared by wet etching using 3% HF solution in terms of thickness and roughness factors. Sensing performance of nanoporous Pt films prepared by XeF2 dry etching was as good as that of wet-chemically dealloyed nanoporous Pt films for glucose sensing.

Application of Nano Texturing on Multi-Crystalline Silicon Solar Cells

Nano texturing has been confirmed as an effective structure to improve the efficiency of multi-crystalline silicon solar cells by reducing optical loss. In this study, nano textured solar cells are fabricated by the Reactive Ion Etching (RIE) method based on a conventional production line. Several characterization methods are employed to evaluate the morphology, minority carrier lifetime, quantum efficiency and electricity performance of both nano textured and micro textured solar cells. The results show that nano textured solar cells have a maxiumum efficiency of 19.21 % and an average efficiency that is 0.57 % higher than that of micro textured solar cells. Thus, the RIE method is an effective way to manufacture nano textured solar cells. It can demonstrably improve the photoelectric conversion efficiency of mass-produced solar cells and reduce the production cost, which is significant to the development of solar cell industy. DOI: http://dx.doi.org/10.5755/j01.ms.24.2.17398

High Mobility Anisotropic Black Phosphorus Nanoribbon Field‐Effect Transistor

AbstractAchieving excellent electrostatic control and immunity to short channel effects are the formidable challenges in ultrascaled devices. 3D device architectures, such as nanoribbon, have successfully mitigated these problems by achieving uniform top‐ and side‐wall control of the channel. Here, by leveraging on the merits of 3D structure, high‐mobility black phosphorus nanoribbon field‐effect transistors (BPNR‐FET) are demonstrated and the anisotropic transport properties are systematically investigated. A simple top‐down reactive ion etching method is used to realize both armchair‐ and zigzag‐oriented nanoribbons with various widths down to 60 nm. The mobility of BPNR‐FET is found to be width‐ and thickness‐dependent, with the highest hole mobility of ≈862 cm2 V−1 s−1 demonstrated in armchair‐oriented device at room temperature by combining high‐κ gate dielectric and hydrogen treatment to reduce sidewall scattering. Furthermore, hydrogenation effectively passivates the nanoribbon dangling bonds, leading to hysteresis and contact resistance improvement. This work unravels the superior electrical performance underscore a conceptually new device based on BP nanoribbons, paving the way toward the development of nonplanar devices on 2D materials platform.

A Novel Approach to Realize Si-Based Porous Wire-In-Tube Nanostructures for High-Performance Lithium-Ion Batteries.

Hollow inorganic nanostructures have drawn great attention due to their fascinating features, such as large surface area, high loading capacity, and high permeability. The formation, characterization, and application of partially and entirely hollow structure by applying a Si-based reactive ion deposition and etching method on silicon nanowire as a template are reported. This fabrication technique is extended to a stainless steel substrate to be used as the binder-free anode for high capacity and high rate lithium-ion batteries. The electrochemical analyses exhibit that in addition to the high initial discharge capacity of 4125 mAh g-1 at a rate of C/16, the best performing electrode shows discharge/charge capacity of as high as 3302.14/2832.1 mAh g-1 , respectively, with an excellent charge capacity retention of 96.7% over 100 cycles at a rate density of 1 C. Even at a rate of 12 C, the as-designed structure is still able to deliver an impressive 1553 mAh g-1 , which probably is attributed to fast lithium diffusion in its hollow part and high porosity of Si and alumina layer. It is proved that the change in hollowness ratio significantly affects capacity retention and average coulombic efficiency of the lithium-ion cells.

Nanoladders Facilitate Directional Axonal Outgrowth and Regeneration.

After injuries, axonal regeneration over long distance is challenging due to lack of orientation guidance. Biocompatible scaffolds have been used to mimic the native organization of axons to guide and facilitate axonal regeneration. Those scaffolds are of great importance in achieving functional connections of the nervous system. We have developed a nanoladder scaffold to guide directional outgrowth and facilitate regeneration of axons. The nanoladders, composed of micron-scale stripes and nanoscale protrusions, were fabricated on the glass substrate using photolithography and reactive ion etching methods. Embryonic neurons cultured on the nanoladder scaffold showed significant neurite elongation and axonal alignment in parallel with the nanoladder direction. Furthermore, the nanoladders promoted axonal regeneration and functional connection between organotypic spinal cord slices over 1 mm apart. Multimodality imaging studies revealed that such neuronal regeneration was supported by directional outgrowth of glial cells along nanoladders in the organotypic spinal cord slice culture as well as in the coculture of glial cells and neurons. These results collectively herald the potential of our nanoladder scaffold in facilitating and guiding neuronal development and functional restoration.

High-Performance MIM Capacitors for a Secondary Power Supply Application.

Microstructure is important to the development of energy devices with high performance. In this work, a three-dimensional Si-based metal-insulator-metal (MIM) capacitor has been reported, which is fabricated by microelectromechanical systems (MEMS) technology. Area enlargement is achieved by forming deep trenches in a silicon substrate using the deep reactive ion etching method. The results indicate that an area of 2.45 × 103 mm2 can be realized in the deep trench structure with a high aspect ratio of 30:1. Subsequently, a dielectric Al2O3 layer and electrode W/TiN layers are deposited by atomic layer deposition. The obtained capacitor has superior performance, such as a high breakdown voltage (34.1 V), a moderate energy density (≥1.23 mJ/cm2) per unit planar area, a high breakdown electric field (6.1 ± 0.1 MV/cm), a low leakage current (10−7 A/cm2 at 22.5 V), and a low quadratic voltage coefficient of capacitance (VCC) (≤63.1 ppm/V2). In addition, the device’s performance has been theoretically examined. The results show that the high energy supply and small leakage current can be attributed to the Poole–Frenkel emission in the high-field region and the trap-assisted tunneling in the low-field region. The reported capacitor has potential application as a secondary power supply.

Texturization of ZnO:Al surface by reactive ion etching in SF6/Ar, CHF3/Ar plasma for application in thin film silicon solar cells

As-deposited sputtered ZnO:Al (AZO) thin films having high transparency (T ≥ 85% at 550 nm of wavelength) and good electrical properties (ρ = 2.59 × 10−04 Ω cm) are etched to get suitable light trapping in thin film solar cells, using reactive ion etching method in sulfur hexafluoride–argon (SF6/Ar) plasma and trifluoromethane–argon (CHF3/Ar) plasma to texture their surface. Though the electrical properties of the films are not affected much by the etching process but significant increment in the average haze values in the wave length range of 350–1100 nm in the etched AZO films (19.21% for SF6/Ar and 22.07% for CHF3/Ar plasma etched) are found compared to as-deposited AZO films (5.61%). Increment in haze value is due to more scattering of light from the textured surface. These textured substrates are used as front transparent conducting oxide electrode for the fabrication of amorphous silicon solar cells. Solar cells fabricated on etched AZO substrates show 7.76% increase in conversion efficiency compared to as-deposited AZO substrates.

Optimization of surface reflectance for silicon solar cells

A study on the formation of black silicon (b-Si) antireflection layers on crystalline Si wafers using SF6/O2gas mixture in a reactive ion etching method is presented. The process is low-temperature, fast and does not depend on the crystallographic orientation of the Si wafer. The b-Si layers have demonstrated average reflectance values of 4% and 5% for monoand polycrystalline Si wafers respectively, feature that is suitable for the fabrication of high efficiency solar cells. Passivation of b-Si antireflection layers by suitable different thin films can significantly reduce needle-like surface recombination losses.

Fabrication and evaluation of titanium alloy scalpel by Thermally assisted Reactive Ion Etching method

Fabrication and evaluation of titanium alloy scalpel by Thermally assisted Reactive Ion Etching method