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Crystallographically oriented porous ZnO nanostructures with visible-blind photoresponse: controlling the growth and optical properties
摘要： We have grown catalyst-free crystallographically oriented porous ZnO nanostructures by pulsed laser deposition (PLD) method. The deposition was performed in two stages for each sample. In the first stage, self-seeding of ZnO was performed on the quartz substrate, and the angle of deposition (seeding-angle) was varied. Thus, the growth of seeds is different here. In the second stage, the deposition was performed at a glancing angle (at 85?) for the fixed duration of time to grow the nanostructures. These PLD-grown nanostructures acquire highly oriented wurtzite structure. We find that the seeding-angle during the first stage is the determining deposition parameter which influences the growth and other properties of these nanostructures in a controllable manner. The variation in seeding-angle systematically tunes the crystallographic orientation and porosity, which in turn influences the visible-blindness and ultraviolet (UV) photoresponse of these nanonetworks. Here we report the growth of completely defect-free crystallographically oriented nanostructures with necessary porosity for application in visible-blind UV photodetection.
关键词： Crystalline ZnO,catalyst-free ZnO,glancing angle deposition (GLAD),seeding,pulsed laser deposition (PLD),nanostructures
更新于2025-11-21 11:03:13
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Characterisation of AlN nano thin films prepared by PLD
摘要： Aluminium nitride (AlN) nano thin films have been prepared by pulsed laser deposition (PLD) in this paper. The microstructure and grain size of the nano thin films were characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the PLD conditions such as laser fluence, ambient pressure and substrate temperature influence the thickness, morphology and grain size of the nano thin films obviously, i.e. the surface of the nano thin films becomes rough while the grain size increases with increasing the laser fluence, ambient pressure and substrate temperature. In addition, there exists a preferred orientation growth in the thin films.
关键词： microstructure,pulsed laser deposition (PLD),aluminium nitride,grain size,Nano thin films
更新于2025-09-23 15:22:29
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Development of Pd/TiO2 Porous Layers by Pulsed Laser Deposition for Surface Acoustic Wave H2 Gas Sensor
摘要： The influence of sensitive porous films obtained by pulsed laser deposition (PLD) on the response of surface acoustic wave (SAW) sensors on hydrogen at room temperature (RT) was studied. Monolayer films of TiO2 and bilayer films of Pd/TiO2 were deposited on the quartz substrates of SAW sensors. By varying the oxygen and argon pressure in the PLD deposition chamber, different morphologies of the sensitive films were obtained, which were analyzed based on scanning electron microscopy (SEM) images. SAW sensors were realized with different porosity degrees, and these were tested at different hydrogen concentrations. It has been confirmed that the high porosity of the film and the bilayer structure leads to a higher frequency shift and allow the possibility to make tests at lower concentrations. Thus, the best sensor, Pd-1500/TiO2-600, with the deposition pressure of 600 mTorr for TiO2 and 1500 mTorr for Pd, had a frequency shift of 1.8 kHz at 2% hydrogen concentration, a sensitivity of 0.10 Hz/ppm and a limit of detection (LOD) of 1210 ppm. SAW sensors based on such porous films allow the detection of hydrogen but also of other gases at RT, and by PLD method such sensitive porous and nanostructured films can be easily developed.
关键词： bilayer films,pulsed laser deposition (PLD),palladium,hydrogen sensor,surface acoustic wave (SAW),Pd/TiO2,porous morphology,titanium dioxide
更新于2025-09-23 15:19:57
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In situ laser reflectivity to monitor and control the nucleation and growth of atomically-thin 2D materials
摘要： The growth of atomically-thin two-dimensional (2D) layered and other quantum materials is typically performed without in situ monitoring or control. Here, a simple laser reflectivity approach is demonstrated to provide in situ control over sub-monolayer thickness and growth kinetics during pulsed laser deposition (PLD) of MoSe2 layers. First, the general technique is presented with emphasis on designing the maximum sensitivity of the optical contrast through consideration of Fresnel’s equations with proper choice of layer thickness, substrate, and laser monitoring wavelength, incidence angle, and laser polarization. Then the 633 nm optical reflectivity of MoSe2 layers on SiO2/Si substrates was predicted and compared with in situ monitoring of MoSe2 growth by PLD under actual growth conditions using a probe HeNe laser beam. The measurements showed high sensitivity and excellent agreement with MoSe2 surface coverages calculated from atomic resolution STEM analysis of 2D layers deposited in arrested growth experiments. Growth kinetics revealed by these measurements showed sigmoidal nucleation and growth stages in the formation of the 2D MoSe2 layers that are described by a simple model, indicating the promise of the laser reflectivity technique for in situ monitoring and control of 2D materials deposition.
关键词： pulsed laser deposition (PLD),MoSe2,kinetic modeling,in situ reflectivity,2D materials
更新于2025-09-16 10:30:52
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Pure carbon conductive transparent electrodes synthetized by a full laser deposition and annealing process
摘要： One of the biggest challenge that face optoelectronic and photovoltaic devices is the necessity to provide a reliable alternative to transparent conducting oxide (TCO) like Indium Thin Oxide (ITO). We recently published a study proposing a method to produce transparent conductive electrodes only based on carbon materials. In a first step, we use the Pulsed Laser Deposition (PLD) to produce high performance DLC. Those thin films own very interesting properties in kindship with diamond, like high transparency in the visible range, chemical inertness and biocompatibility. In addition, the DLC is a perfect electrical insulator and presents a relative high opacity in ultra-violet (UV). This particularity has a great interest to perform, in a second step, UV laser annealing over the DLC surface. The aim is to break the existing diamond bindings (sp3 hybridization) on the surface and allow atoms being reorganized in graphitic bindings (sp2 hybridization). We demonstrate that the increase of atomic graphitic bindings leads to a valuable surface conductivity. According to optimized annealing parameters, the surface conductivity reaches values comparable to ITO. We also show that the laser treatments only sparsely affects the DLC transparency. Moreover, this full laser-based process remains compatible with the standard microelectronic technological steps.
关键词： Diamond-Like Carbon (DLC),Graphitization,Pulsed Laser Deposition (PLD),Transparent electrodes,Laser surface annealing
更新于2025-09-12 10:27:22
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Nitric Oxide Detector Based on WO <sub/>3</sub> -1wt%In <sub/>2</sub> O <sub/>3</sub> -1wt%Nb <sub/>2</sub> O <sub/>5</sub> with State-of-the-Art Selectivity and ppb-Level Sensitivity
摘要： Fast, sensitive, and precise detection of nitric oxide (NO) is critical to many applications in environmental monitoring and early disease diagnosis via respiratory testing. An effective detection system requires a sensor to detect NO gas at the parts per billion (ppb) level, and this system should possess a high degree of anti-interference selectivity. To achieve these targets, a series of gas sensor thin films based on intrinsic WO3, one-additive-doped WO3 (prepared by doping In2O3 or Nb2O5), and two-additive-doped WO3 (synthesized by doping with In2O3 and Nb2O5) oxides were successfully grown. By analyzing the properties of sensitivity, selectivity, responsiveness, and recovery time of the gas sensors, we found that WO3-1wt%In2O3-1wt%Nb2O5 has overwhelming advantages over intrinsic WO3, WO3-In2O3, and WO3-Nb2O5. A sensing response value of 2.4 was observed for NO concentrations as low as 20 ppb from the WO3-1wt%In2O3-1wt%Nb2O5 sensor. With 100 ppb NO gas, the WO3-1wt%In2O3-1wt%Nb2O5 sensor achieved a high response of 56.1 at 70 °C, which is a state-of-the-art performance for NO detection at low working temperature settings. WO3-1wt%In2O3-1wt%Nb2O5 also yields significantly improved selectivity and stability over intrinsic WO3, WO3-In2O3, and WO3-Nb2O5. Studies on the sensing mechanism show that the grain size, rather than the n?n heterostructure effect, plays a dominant role in the observed results. By decreasing the grain size so that it is close to the thickness of the space-charge layer, the sensing response is enhanced. Although room remains to further improve the sensing properties, the performance of WO3-1wt%In2O3-1wt%Nb2O5 is sufficient for implementation in low-content NO detection devices.
关键词： codoping,high selectivity,NO gas sensor,limit of detection (LOD),ppb-level response,pulsed laser deposition (PLD)
更新于2025-09-09 09:28:46