The high thermal budget of three-dimensional NAND Flash (3D NAND Flash) is the key issue limiting the increase in vertical integration. The main purpose of this article is to design a local and high ...temperature annealing function to reduce the thermal budget and gain a high activation rate without diffusion at a target depth to improve the performance of 3D NAND Flash devices by laser annealing with green wavelength. The method of nanosecond pulse laser annealing (ns-PLA) for amorphous silicon (a-Si) crystallization and activation has been proven, and this method has the benefits of a low thermal budget and controllable heating. According to previous experiments, one of the important results is that ns-PLA with high energy can provide a high temperature that reaches the melting point of a-Si and obtain a deep and monocrystal-like silicon channel through liquid phase crystallization in 3D NAND applications and obtain a higher activation rate. These results cast emerging light on low thermal budget processes based on ns-PLA in 3D NAND flash for future architecture such as Xtacking architecture, and have significant ramifications for impurity activation rates and reducing channel leakages.
Fiber-optic laser-induced breakdown spectroscopy (LIBS) can be used for on-site chemical analysis in harsh environments with a flexible light delivery system. In this work, the use of a long-pulse ...laser (100 ns) is proposed for the detection of molecular emission signals, instead of a normal-pulse laser (6 ns). We show a significant enhancement of AlO signals using an aluminum metal target in air. We also elucidate the enhancement mechanism of the AlO formation by measuring species-specific images of the emission from aluminum atoms, oxygen atoms, and AlO molecules in the plasma. The internal structure of the plasma suggests that the formation origin of AlO molecules in the long-pulse-produced plasma is essentially different from that in the normal-pulse-produced plasma. The long-pulse laser causes a rise of the ablation plume and facilitates the flow of oxygen from the ambient air. This is a key factor to enhance the molecular emission signals.
Display omitted
•Fiber-optic LIBS of Al metal in air was performed with 6-ns or 100-ns pulse laser.•AlO signals were significantly enhanced by using the long-pulse laser.•Emission regions of Al atoms, O atoms, and AlO molecules were investigated.•AlO emission was observed at the side edge of the normal-pulse-produced plasma.•AlO emission was observed at the bottom of the long-pulse-produced plasma.
To realize detection of moving vehicles, the pulsed laser circular-viewing system is proposed. The principle of system is described. The scanning detection model of laser circular-viewing system is ...established based on best matching principle. The maximum range and minimum motor speed are deduced. Laser ranging system and azimuth detection system are designed. The system is fabricated to test. The experiments demonstrate that emission system is adjustable, and laser ranging error is within ±0.2m. The system possesses overload capacity at a certain degree.
In this study deposited zinc oxide (ZnO) nanostructures were prepared by pulsed laser deposition (PLD) technique on porous silicon (PS) substrates that were prepared via photoelectrochemical etching ...of silicon n-type (100). The study investigated the influence of laser energy on various characteristics of the fabricated devices, including their optical, morphological, structural, electrical, and photodetector features. The X-ray diffraction results indicate a dominant broad diffraction peak at 69.14°, and the ZnO phase aligns with the hexagonal wurtzite structure. The field emission scanning electron microscopy micrograph illustrates that porous silicon has a sponge-like fashion, while ZnO nanostructures have spherical grains distributed randomly and grow larger with laser energy. The optical characteristics of the manufactured samples were examined using techniques that include UV–vis absorption spectroscopy, UV–vis diffuse reflectance spectrometry, and photoluminescence spectroscopy. The findings indicated that decreased laser energy led to a blue shift in the energy gap. The reflectivity of the produced samples decreased after the deposition of a zinc oxide layer over porous silicon. The photoluminescence examination showed the presence of four distinct emission peaks, namely, UV, violet-blue, blue, and green, consequent to coating a ZnO layer onto the porous silicon substrate. Fourier transform infrared spectroscopy confirmed that ZnO thin films deposited on porous silicon cause surface oxidation and produced a new peak at 455.2 cm
−1
related to the Zn–O stretching band. The current density–voltage properties of the fabricated devices in the absence and presence of white light were investigated as a function of laser energy. The ZnO NPs/PS/n-Si photoreactors displayed rectifier features and had outstanding spectral responsivity from ultraviolet to near-infrared. Moreover, the fabricated photoreactor showed the most prominent external quantum efficiency (EQE) in the UV region. The results of this study are of great importance to the advancement of photodetectors and optoelectronic devices based on ZnO and porous silicon.
Surface modification processes of any metallic structure with the help of laser irradiation are a universal practice. The profoundly focused laser beam is to irradiate on the substrate surface to ...modify the surface condition for the improvement of the tribological properties in heavy and rouged engineering applications. There is a wide application of pure or raw Ti in the field of the biomedical sector specifically in implants and artificial joint prosthesis. In the viewpoint of the above, the present work determines the thermal characteristic aspect in a pure Ti physical domain by developing a two-dimensional heat transfer approach with the dual-phase-lag (DPL) model under the influence of the ultrashort pulsed laser heating. The physical domain has a Ti nanofilm of the 4 nm length, 2 nm width, and 0.02 nm thickness. A DPL model is developed for analyzing the ultrafast heating, as it is the most potential heat transfer model. The present study has modelled a hybrid analytical analysis comprising of the Duhamel’s theorem and the finite integral transform method. This work highlights the essentiality of applications of the DPL heat conduction model over the conventional Fourier’s model based on the qualitative assessment. The selection of thermal relaxation time lags was carefully chosen from the existing experimental evidence due to the requirement to reach the melting point temperature of pure Ti. The peak temperature of laser irradiation declines with the increase in the optical penetration depth and laser pulse time. Finally, the competence of the present analysis is validated with the published numerical and experimental works from the engineering accuracy standpoint.
The control of oxygen vacancy channels (OVCs) in brownmillerite (BM) oxides has a substantial impact on tuning their physical and chemical properties. Here, we demonstrated a strain mechanism for ...directing the OVCs in BM-SrFeO2.5 (SFO) synthesized via a two-step process in which perovskite (P)-structured SrFeO3−δ (P-SFO3−δ) thin film is first prepared and then converted to the BM phase through the post-vacuum-annealing (PVA) treatment. The initial strain state for the first-step-prepared P-SFO3−δ thin films plays a determining role in the orientation of the OVCs of the final BM phase with the systematic manipulation of both chemical strain (lattice expansion) and epitaxial strain by tuning the oxygen deficiency and using different substrates, respectively. Larger tensile strains in the initial P-SFO3−δ thin films are inclined to facilitate the formation of BM with horizontal OVCs after PVA, while small tensile or compressive strains favor the vertical OVCs. Our results offer insights into the selective control of the orientation of the OVCs of BM-SrFeO2.5 thin films, which are of benefit to the design for functionalities related to the ion transport and migration.
We have demonstrated Si implantation incorporation into GaN HEMTs with a non-alloyed ohmic contact process. We optimized the power density of pulsed laser annealing to activate implanted Si dopants ...without a thermal metallization process. The experimental results show that the GaN surface will be reformed under the high power density of the illumination conditions. It provides a smooth surface for following contact engineering and leads to comparable contact resistance. The transmission line model (TLM) measurement shows a lower contact resistance to 6.8 × 10−7 cm2 via non-alloyed contact technology with significantly improved surface morphology of the contact metals. DC measurement of HEMTs shows better current and on-resistance. The on-resistance could be decreased from 2.18 to 1.74 m -cm2 as we produce a lower contact resistance. Pulsed laser annealing also results in lower gate leakage and smaller dispersion under a pulse I-V measurement, which implies that the density of the surface state is improved.
Yb:CaYAlO4 single crystals were grown by the floating zone method and their spectral properties were investigated. Void formation was effectively suppressed by using a feed rod of Y-rich composition ...with the aid of a double zone-pass technique. For the oxygen excess composition of Yb:Ca0.9925Y1.0075AlO4.00375, a void-free crystal was obtained by performing only the double zone-pass. On the other hand, for cation-deficient type of Yb:Ca0.9925Y1.005AlO4, void-free crystal could not be obtained by performing the double zone-pass. The void formation is attributable to the constitutional supercooling caused by segregation of main constituents of Y and Ca, and the congruent composition may exist in the Y-rich region with existence of interstitial excess oxide ions. The absorption cross section for σ-polarization was slightly larger than that for π-polarization, which is reasonable on the basis of the crystal structure of CaYAlO4.
•Yb:CaYAlO4 single crystals were grown by the floating zone method.•The void formation is attributable to the constitutional supercooling.•The congruent composition may exist in the Y-rich region with existence of interstitial excess oxide ions.•The absorption cross section for σ-polarization was slightly larger than that for π-polarization.
A double pulse laser system that combines Raman spectroscopy and laser induced plasma spectroscopy (LIPS) in a single unit is demonstrated. The study attempts to improve the atomic signals of LIPS ...while simultaneously extracting the desired molecular signals from Raman. In low pressure conditions such as the lunar atmosphere, the detection of plasma emission is difficult due to the low electron density and short persistence time causing a rapid plasma expansion. Moreover, in the integration of the spectroscopic system aimed at space exploration, the system size and weight should be minimized. Simultaneous molecular and atomic detection that gave highly resolved spectra of both LIPS and Raman at pressure below 0.07 Torr is achieved. First, a low-energy laser pulse was used to produce a small plasma and to detect the molecular signals through the inelastic scattering effect. Then, the laser pulse at a higher energy is used to produce a larger plasma plume for detecting the atomic signals. Amongst eight rock samples tested, plasma stacking by generating two sequential plasmas produced from the double-pulse laser on Calcite for example enhanced the signal intensities of calcium and oxygen lines by twofold, compared to a conventional LIPS.
Display omitted
•Double-pulse lasing with inter-delay time is applied to Raman-LIPS detection.•Previous attempts on simultaneous Raman-LIPS have never achieved signal enhancement.•Simultaneous molecular and atomic signals on eight rock samples were detected.•Improved sensitivity and signal enhancement were achieved.
A laser lift-off (LLO) process has been developed for detaching thin InGaN/GaN lightemitting diodes (LED) from their original sapphire substrates by applying an ultrafast laser. LLO is usually based ...on intense UV irradiation, which is transmitted through the sapphire substrate and subsequently absorbed at the interface to the epitaxially grown GaN stack. Here, we present a successful implementation of a two-step LLO process with 350 fs short pulses in the green spectral range (520 nm) based on a two-photon absorption mechanism. Cathodo- and electroluminescence experiments have proven the functionality of the LLO-based chips. The impact of radiation on the material quality was analysed with scanning (SEM) and transmission electron microscopy (TEM), revealing structural modifications inside the GaN layer in some cases.
PDF
