High Vacuum Chamber Research Articles

Enhancing ZnO/Si Heterojunction Solar Cells: A Combined Experimental And Simulation Approach

In this study, we explore the fabrication and optimization of ZnO/Si heterojunction solar cells to enhance their performance through precise control of electron affinity and bandgap properties. ZnO thin films were synthesized using thermal oxidation in a high-vacuum chamber, followed by annealing to improve crystallinity and electrical characteristics. The photovoltaic performance of the ZnO/Si heterojunction solar cells was systematically characterized, and Quantum ESPRESSO simulations were employed to refine the electronic properties of ZnO. Our results show significant improvements in open-circuit voltage, short-circuit current density, and overall conversion efficiency. The optimization of ZnO/Si heterojunction solar cells involves enhancing the electronic properties of ZnO thin films. Quantum ESPRESSO simulations were utilized to optimize the ZnO structure, calculate the band structure and density of states (DOS), and study the effects of Ga and Mg doping on the electronic properties of ZnO. The initial step in our study involved the structural optimization of ZnO to determine its lowest energy configuration. The optimization of the band offset engineering to improve the efficiency of n-ZnO/p-Si photovoltaic cells was found to be critical. Doping ZnO with Ga and Mg improved the band alignment with Si, reduced recombination losses, and enhanced charge carrier mobility. Our findings underscore the potential of optimized ZnO/Si heterojunction solar cells for high-efficiency solar energy conversion, demonstrating their viability as cost-effective and efficient solutions for renewable energy applications. This study highlights the importance of precise material engineering and simulation-driven optimization in developing advanced photovoltaic devices.

Development and Evaluation of Ferrite Core Inductively Coupled Plasma Radio Frequency Ion Source for High-Current Ion Implanters in Semiconductor Applications.

This study presents the development of a ferrite core inductively coupled plasma (ICP) radio frequency (RF) ion source designed to improve the lifetime of ion sources in commercial ion implanters. Unlike existing DC methods, this novel approach aims to enhance the performance and lifetime of the ion source. We constructed a high-vacuum evaluation chamber to thoroughly examine RF ion source characteristics using a Langmuir probe. Comparative experiments assessed the extraction current of two upgraded ferrite core RF ion sources in a commercial ion implanter setting. Additionally, we tested the plasma lifetime of the ICP source and took temperature measurements of various components to verify the operational stability and efficiency of the innovative design. This study confirmed that the ICP RF ion source operated effectively under a high vacuum of 10-5 torr and in a high-voltage environment of 30 kV. We observed that the extraction current increased linearly with RF power. We also confirmed that BF3 gas, which presents challenging conditions, was stably ionized in the ICP RF ion sources.

Preparation of a membrane-sealed cell for studying catalyst nanoparticles in flowing gas with high vacuum x-ray photoelectron spectrometer.

Here a sealing-style x-ray photoelectron spectroscopy study of the surface of a 1.0 wt. %Ni/TiO2 nanoparticle catalyst in a flowing mixture of CO and O2 at 1bar was performed with a graphene membrane-sealed Si3N4 window-based miniature cell. We report the details on how a commercial Si3N4 window is modified before assembling a graphene membrane, how single-layer graphene membranes are transferred from their metal supports to the modified Si3N4 window, how a modified Si3N4 window covered with a double-layer graphene membrane is assembled onto a blank cell cap, how a nanoparticle catalyst is introduced to the cell cap and then the cell cap is installed onto a cell body to form a complete reaction cell, and how a complete cell is interfaced with a high vacuum chamber of an XPS system before an XPS study of 1.0 wt. %Ni/TiO2 catalyst surface in a flowing mixture for 0.2bar CO and 0.8bar O2 is performed. How the characterization of a catalyst using this type of graphene membrane-sealed Si3N4 window-based miniature cell is relevant to the finding of the actual surface chemistry of a catalyst during catalysis is discussed.

Oxygen-termination effect on the surface energy dissipation in diamond MEMS

Single-crystal diamond (SCD) microelectromechanical systems (MEMS) resonators with lower energy dissipation and higher quality (Q) factors have always been pursued for the development of high-sensitivity and high signal-to-noise ratio (SNR) MEMS sensors. The intrinsic loss such as the crystal quality and extrinsic loss of clamping loss have been examined to improve the Q factors of SCD MEMS resonators. Nevertheless, the surface termination induced energy dissipation has rarely been known due to the lack of high crystal quality diamond resonators and in-situ characterization. Here we examine the effect of oxygen-termination on the surface energy dissipation of SCD cantilevers by in-situ heating these cantilevers in a high vacuum chamber. After thermal treatment of the cantilevers at 933 K, the Q factor of the cantilever is improved from 2.8x105 to 3.3x105 (i.e. the 120 μm-long). The resonance frequency increase confirms the desorption of surface adsorbates. Compared to silicon, on which a native solid-state oxide exists, the surface oxygen-termination induced loss in diamond MEMS is much smaller. The non-existence of native oxides on diamond surface is an obvious merit toward ultra-high Q factor MEMS resonators.

A versatile setup for nanosecond laser polishing processes with in situ analysis capabilities.

Laser polishing of material surfaces is a complex process depending on many variable parameters, such as, e.g., the properties of the used laser and optics (wavelength, pulse duration, fluence, and profile), as well as the processing (spot size, feed rate, and line or point overlap), and the thermodynamical properties of the material to be polished (heat capacity, heat conduction, etc.). For the successful laser polishing of any material, a systematic variation of all the process parameters is required to obtain satisfactorily polished surfaces with an appropriate set of parameters for the material of interest. In order to allow systematic studies of laser polishing processes, a new setup employing a highly stable nanosecond laser with an adjustable wavelength has been realized. The sample is located in a small high-vacuum chamber with the capability of introducing additional gases in a controlled manner, and the entire chamber is scanned in the beam to allow laser polishing of selected spots, lines, or larger areas. The setup is fully remote-controlled and allows in situ inspection of the initiated processes by means of a long-range microscope, electrical measurements, reflected laser light from the sample surface, and an analysis of the vacuum within the process chamber. The main properties of the setup will be presented, and some exemplary results on niobium and molybdenum metal samples will be discussed.

LIOVIX® Printable Lithium Technology for Lithium Anode Manufacturing at Scale

The commercialization of lithium metal batteries requires the mass production of cost-effective thin lithium metal foil with thickness less than 30 µm. However, today’s known technologies are not yet commercially available. For example, thin lithium metal foil can be produced by hydraulic extrusion followed by a rolling process. This process usually requires a delicate balance between the pressure and tension created by both extruder and winder, so that the resulting foil is not torn or stretched, retaining all the dimensional characteristics required. This process can be extremely challenging when making lithium metal films with thickness less 20 µm due to the poor mechanical properties of lithium metal. Lithium metal foil can also be produced by physical vapor deposition (PVD). Lithium metal foil produced by PVD process are generally homogenous and have good control in thickness. However, PVD technology requires high vacuum chamber and is slow in the deposition rate, typically in the range of 0.1 to 100 nm s−1, making industrial scale of 20 µm lithium foil very challenging1.Livent has developed LIOVIX®printable lithium technology, a proprietary formulation that combines Stabilized Lithium Metal Powder (SLMP®), rheology modifiers and solvent to produce a stable suspension that can be printed on most common substrates. LIOVIX®printable lithium technology is an enabling technology that can produce thin lithium foil with thickness of 5 µm to 50 µm with no limitation in width, length and at high deposition speed. LIOVIX®enables pattern printing and can be applied to any substrate, for example a prefabricated anode, cathode, current collector, separator, and solid or polymer electrolyte. This technology enables 3D battery printing in a custom form factor shape.In this presentation, we will cover thin lithium foil manufacturing processes using standard industrial equipment and electrochemical performance results.References Acebedo, Begoña, et al. "Current Status and Future Perspective on Lithium Metal Anode Production Methods." Advanced Energy Materials (2023): 2203744.

Characterization in the extreme ultraviolet (XUV) domain of microchannel plate based device using synchrotron radiation

Innovative, low-loss, and compact optical systems are essential to meet the experimental requirements of emerging novel radiation sources. The microchannel plate (MCP), a metamaterial-based optical device, shows promising potential for shaping, condensing, and focusing soft x-ray radiation at synchrotron radiation (SR) facilities. This study highlights the impact of MCP optical devices on SR beam condensing capability and their sensitivity to the degree of coherence by investigating the profile of transmitted beams through single and double MCP optical devices. Transmitted diffraction patterns of soft x-ray SR radiation change with energy and radiation modes. At 92 eV, the double MCP-based device affects the beam divergence and degree of coherence more than the single MCP. Moreover, the double MCP device shows potential as a condensing optics at shorter wavelengths, i.e., 480 eV. Experiments were performed at the available end-station of the Circular Polarization beamline at the Elettra synchrotron facility in Trieste, using a high-vacuum chamber with a hexapod system, providing the precise movement necessary to align these diffractive optics. The findings contribute to the development of innovative optical systems for SR and free-electron laser beamlines, paving the way for advanced experiments in spectroscopy, microscopy, and imaging in a wide energy range.

Space Silicone Adhesive Monitoring Via Minimally Intrusive Optical Fibre Sensing During Vacuum UV/VUV Radiation Exposure

In this work a technique to monitor the health state of space adhesives during environmental testing is presented. Specifically, minimally intrusive Tilted Fibre Bragg Grating (TFBG) sensor was embedded in silicone adhesive Nusil CV16-2500 used to bond two thin cover glasses. The resulting solar cell assembly was then exposed to the UV/VUV radiation in a high vacuum chamber (less than 10-5 mbar). The sensor is demonstrated that it was able to measure simultaneously the strain, temperature and refractive index of the adhesive. The three parameters measured with the TFBG, can be used to detect the thermomechanical and refractometric state of the silicone adhesive.

Interaction Study of Energetic Protons and Electrons with the Vacuum Ultra Violet Source used in the Complex Irradiation Facility

Context: One important factor to be considered for space missions is the radiation environment. It is composed of energetic particles, such as protons, electrons and ions, and electromagnetic radiation, photons ranging from Vacuum Ultra Violet (VUV) to Far Infrared (FIR). Each of these radiation sources have an unique energy spectrum that further depends on the location inside the solar system, e. g. Earth orbits or interplanetary space.For material qualification and material engineering, individual irradiation is considered and their effects are superimposed. However, effects occurring when two and more radiation types simultaneously are present have barely been investigated yet. Further complexity is added, when additional interactions take place due to laboratory hardware. Aims: This publication reports on the efforts made to analyse and measure the interaction of a VUV and corpuscular radiation sources. The aim is to quantify the deviations due to interactions and conclude consequences for the simultaneous operation of these radiation sources. Methods: In order to quantify the effects, the Complex Irradiation Facility (CIF), located at the DLR Bremen has been used. It connects proton and electron accelerators together with VUV and UV light sources to an ultra high vacuum chamber. The corpuscular and VUV radiation sources have been operated simultaneously. The reaction of the operation parameters, such as current measured with Faraday Cups (FC) has been tracked and post-processed. Results: It has been discovered, that protons considerably interact with the gas mixture used to operate the VUV source. This interaction decreases for higher beam intensities of the corpuscular irradiation. It was found, that this is likely due to protons ionizing gas atoms which are then measured by the FC as current. For electrons, this phenomena was not observed due to their smaller stopping power. The discovery restricts the acceleration factor of the CIF for proton together with VUV irradiation, but does not necessarily limit the range of application of the CIF depending on the requirements of the material and/or qualification test. Energy range of electrons stays unrestricted.

Formation Pathways of Lath-Shaped WO3 Nanosheets and Elemental W Nanoparticles from Heating of WO3 Nanocrystals Studied via In Situ TEM.

WO3 is a versatile material occurring in many polymorphs, and is used in nanostructured form in many applications, including photocatalysis, gas sensing, and energy storage. We investigated the thermal evolution of cubic-phase nanocrystals with a size range of 5-25 nm by means of in situ heating in the transmission electron microscope (TEM), and found distinct pathways for the formation of either 2D WO3 nanosheets or elemental W nanoparticles, depending on the initial concentration of deposited WO3 nanoparticles. These pristine particles were stable up to 600 °C, after which coalescence and fusion of the nanocrystals were observed. Typically, the nanocrystals transformed into faceted nanocrystals of elemental body-centered-cubic W after annealing to 900 °C. However, in areas where the concentration of dropcast WO3 nanoparticles was high, at a temperature of 900 °C, considerably larger lath-shaped nanosheets (extending for hundreds of nanometers in length and up to 100 nm in width) were formed that are concluded to be in monoclinic WO3 or WO2.7 phases. These lath-shaped 2D particles, which often curled up from their sides into folded 2D nanosheets, are most likely formed from the smaller nanoparticles through a solid-vapor-solid growth mechanism. The findings of the in situ experiments were confirmed by ex situ experiments performed in a high-vacuum chamber.

Correlative high-resolution imaging of hydrogen in Mg2Ni hydrogen storage thin films

Nanometer scale imaging of hydrogen in solid materials remains an important challenge for the characterization of advanced materials, such as semiconductors, high-strength metallic alloys, and hydrogen storage materials. Within this work, we demonstrate high-resolution imaging of hydrogen and deuterium within Mg2Ni/Mg2NiH4 hydrogen storage thin films using an in-house developed secondary ion mass spectrometer (SIMS) system attached to a commercially available dual-beam focused ion beam - scanning electron microscope (FIB-SEM) instrument. We further demonstrate a novel approach to measure the size, shape, and distribution of the hydride phase in partially transformed films using laser scanning confocal microscopy (LSCM) to measure surface topography changes from the hydride phase volume expansion. Combining these techniques provides new insights on hydride nucleation and growth within the Mg2NiHx system. Finally, we demonstrate the efficacy of tracking deuterium as a hydrogen analog to reduce the background for SIMS imaging of hydrogen in high-vacuum chambers (∼10−6 mbar).

Characterization of X-Ray Events in a Vacuum High Voltage Long-Gap Experiment

The high voltage Padova test facility (HVPTF) is an experimental device for the study of HV insulation in vacuum, in support of the realization of the prototype of a neutral beam injector for International Thermonuclear Experimental Reactor (ITER), named megavolt ITER injector and concept advancement (MITICA). The facility investigates the physical phenomena underlying voltage holding in vacuum, in particular the mechanisms causing breakdowns and the electrode conditioning process. At HVPTF, inside a high vacuum chamber, two stainless steel electrodes, separated by a few centimeters gap, can achieve HV values for a maximum potential difference of 800 kV. During the voltage conditioning of the electrodes, current MicroDischarges (MDs) and high-energy X-rays are observed and analyzed. In this work, we present a characterization of the MD dynamics occurring during the conditioning process, with the aim to gain information on the reason of the growing difference between the current contributions measured by the two electrodes. The analysis will be performed due to two new X-rays detectors recently installed: an lutetium yttrium orthosilicate (LYSO) and a LaBr3(Ce) scintillating crystal. The new diagnostics indeed provide the fine dynamics of a single MD, recording energy and time of each single detected X-ray. In particular, we compare the MD dynamics at the beginning and at the end of the conditioning process and try to give a preliminary interpretation of the observations.

Development of ionic liquid circulation system in high-vacuum chamber for semiconductor device fabrication

In this study, a high-vacuum-compatible liquid circulation system was developed using an ionic liquid with a very low vapor pressure as the working fluid. The rationale for the development of this device is the increasing need for wet processing under vacuum conditions for application to semiconductor fabrication, such as developing and rinsing. Wet processes generally use a large volume of liquid; therefore, they need to be conducted under atmospheric pressure. However, vacuum-compatible wet processes are desirable because high vacuum is beneficial for cleanliness and use of beam progression in fabrication processes. Therefore, a liquid circulation system that can be directly used under a high vacuum is needed. The system developed in this study can circulate over 100 mL ionic liquid under direct vacuum exposure, regardless of the inner chamber pressure. The usefulness of a prototype of this system was experimentally investigated. The system reached an ultra-high vacuum pressure of 10−5 Pa. Outgassed ionic liquid fragments were detected with low partial pressures of the order of <10−6 Pa. We concluded that this device can be exploited for semiconductor fabrication application.

In Situ High-Temperature TEM Observation of Inconel Corrosion by Molten Chloride Salts with N2, O2, or H2O

In situ transmission electron microscopy (TEM) diffraction and imaging techniques are used to monitor and quantify corrosion of Inconel-625 by pure molten chloride salts (MgCl2 − NaCl − KCl) at 500 °C–800 °C in 1.0 atm inert N2 or pure O2, or by salts which are controllably hydrated in a high vacuum chamber. The isothermal corrosion rate R in inert N2 increases from 203 ± 30 μm year−1 at 700 °C to 463 ± 30 μm year−1 at 800 °C. An oxygen ambient causes a six-fold increase to R = 1261 ± 170 μm year−1 at 700 °C. Salt hydration dramatically accelerates corrosion to R> 3 × 105 μm year−1 at 700 °C while it leads to a more moderate R = 95 ± 20 and 486 ± 30 μm year−1 at 500 °C and 600 °C, respectively. These isothermal corrosion rates indicate that the molten chloride corrosion is significantly accelerated by salt hydration at temperatures above 600 °C, where corrosion is aggravated by increased generation and solubility of corrosive HCl gases. Hence, to reduce rate of corrosion it is important to both avoid incorporation of H2O into the system at each stage and ensure proper flushing of the system before increasing the temperature beyond 600 °C. Compositional analysis of the corroded cells indicate that corrosion in O2 ambient is dominated by oxidation of metals by O2 gas dissolved in the chloride melt, but corrosion in H2O ambients is caused by chlorination of metals by dissolved HCl gas and MgOH+ ions. So, to reduce rate of corrosion, steps should be taken to tailor chloride melt compositions that has low solubility for HCl and O2. All of our corroded samples exhibit passive-protective oxide layers of Cr, Mg, and Ni. In addition, distinct volatile compounds of Ni, Mo and Cr involving NiCl2, (Na,K)2MoO4 and CrO2(OH)2 are detected in N2, H2O, and O2 ambients, respectively. We believe that corrosion acceleration can be minimized by minimizing formation of volatile by-products or promoting reactions that could convert these volatile compounds to solid phases, as these volatile compounds led to destruction of protective oxide layers.

Nonevaporable getter-MEMS for generating UHV conditions in small volumina

The industrial use of quantum sensors requires further miniaturization of the experimental peripherals, i.e., the high vacuum chamber, laser technology, and control electronics. A central part of the high vacuum chamber is the maintenance of vacuum conditions. For this purpose, a prototype of a compact, i.e., miniaturized, ultrahigh vacuum pump in the form of a nonevaporable getter (NEG) pump at a wafer level (MEMS), is developed within the scope of this work. With regard to the basic conditions of the functionality of the NEG, a miniaturized heating plate with temperature sensors is analytically and numerically developed, constructed, and characterized in an ultrahigh vacuum test stand. This is followed by the integration of the NEG into the existing system, which, in connection with the characterization of material-specific parameters, enables a first correlation of heat input and pumping power. Thus, performance data of the getter-MEMS under high-vacuum confinement confirm its usability for quantum sensors. In addition, optimization potentials are shown with regard to all partial aspects of the MEMS.

Calorimetric testing of solar thermal absorbers for high vacuum flat panels

Among solar thermal collectors, the evacuated flat panel is emerging as a reference technology for operation at temperatures as high as 200 °C with an increased annual energy production owing to both direct and diffuse light capture. Accurate measurements of the optical properties of the selective absorbers used in such devices are key for a reliable estimation of the overall performance. These optical properties must be measured under high vacuum at high temperatures, conditions under which the panels are meant to operate. In this study, we accurately measured these properties using a calorimetric technique. The measurement procedure is based on a power balance equation for a flat sample absorber suspended in a high-vacuum chamber with minimized thermal losses and is well adapted for this class of devices. Calorimetric measurements obtained under Sun and LED light illumination revealed excellent reproducibility and good agreement with those obtained using traditional optical analysis at low temperatures in air. When extended up to the absorber stagnation temperature, which often exceeds 300 °C, the calorimetric measurements started to deviate from the optical measurements, indicating the importance of measuring under actual operating conditions.

Spatial filtering of Zeeman sub-states in an atomic fountain.

In an atomic fountain, atoms in motion can be spatially separated into discrete Zeeman sub-states by magnetically induced Stern-Gerlach effect. With resonant light pulses acting as a shutter, specific states are selected for subsequent experiments. Such separation-selection process in atomic optics is the analogue of a spatial filter in physical optics which selects and purifies the modes of light. This technique is demonstrated by injecting a pulsed current in a circular coil around a vertical atomic fountain, separating the pre-cooled Rubidium atoms by a distance of centimeters in between, and filtering each single sub-state with block pulses. The filtered atoms after the process is highly purified in the desired sub-state. The apparatus of the atomic spatial filter is adaptable in atomic optics and can be integrated into the high-vacuum chamber of an atomic fountain.

Experimental setup to fabricate Rb–Xe gas cells for atom spin gyroscopes

An experimental setup to fabricate atomic vapor cells for atom spin gyroscope application, containing 87Rb, 129Xe, 131Xe, N2, and H2, is described. The setup comprises a high-vacuum chamber, an 87Rb ampule, a glass cell, gas lines, and a turbopump. First, the glass cell is baked for a week at 450 °C to reduce outgassing from the inner walls of the glass cell. Next, rubidium atoms are evaporated into the cubic glass cell. Then, the cubic glass cell is cooled to 2 °C to increase the amount of 87Rb in the cubic glass cell while the vacuum chamber is heated to 100 °C. 6 Torr of 129Xe, 48 Torr of 131Xe, 140 Torr of N2, and 24 Torr of H2 are injected into the cubic glass cell. The sealing method employs pinch-off glass welding. The transverse spin relaxation times of 129Xe and 131Xe at a magnetic field of 6.2 µT applied to the quantization axis are measured to be 8.1 and 16.5 s, respectively, at a cell temperature of 96 °C using nuclear magnetic resonance spectroscopy. The pressure ratio between 129Xe and 131Xe is determined by comparing the output signals from our atom spin gyroscope. The signal-to-noise ratios are 2500 for 129Xe and 3333 for 131Xe, respectively, and the expected angular random walk of the atom spin gyroscope is 0.062°/h1/2 with a 1-Hz repetition rate.

Accurate monitoring of gas mixture transport kinetics through polymeric membranes

• Membrane permeation of CO 2 – rich gas mixture with many gaseous components. • Procedure to monitor mixture transport kinetics by quadrupole mass spectrometer (QMS). • Procedure to resolve the permeation flux of components with overlapping QMS signal. • High accuracy in the measure of penetrant diffusivity and permeability values. • Evidence of plasticization and competitive sorption processes. The accurate assessment of the membrane gas separation properties requires improved metrologies when the feed gases are mixtures rich of components such as biogases, flue gases and mixtures produced by CO 2 reforming. We present an original mass spectroscopy- based approach that permits to monitor the permeation kinetics of gas mixtures formed by components with overlapping mass signals. In the instrumental setup, sample-holder and quadrupole mass spectrometer are hosted in an Ultra High Vacuum chamber which is kept under dynamic pumping conditions during the experimental run. This setup permits to measure, as a function of time, the permeation flux of each mixture component, monitoring kinetics with transient lasting down to the ~ 1 s order. The flux detection limit is 10 -6 cm 3 (STP) m −2 s −1 for species with unambiguously attributable mass signal and no worse than 10 -5 cm 3 (STP) m −2 s −1 for species with overlapping mass signal. Tests were carried out at room temperature with ~ 50 μm thick polymer films exposed to CO 2 - rich gas mixtures at total pressure below 10 5 Pa. The analysis of permeation flux kinetics allows the evaluation of the diffusion constant of migrating species with ~ 4 % indetermination. In steady-state conditions the permeation flux through a poly(lactic acid) film is measured with accuracy better than ~ 3 % for components with unambiguously attributable mass signal ( CO 2 , O 2 ) and no worse than ~ 6 % for those with overlapping mass signal ( N 2 , CO ).

On the opportunity of Laser Plasma simulation of Plasma Jets formation in moderate magnetic fields ∼ kGs

Today a number of various experiments with Laser-Produced Plasmas (LPP), done at very-high Magnetic Fields (up to B0 > MG) are using to model the physics of Astrophysical and Space Jets, a various processes of their formation and possible long-range propagation at various angles S to magnetic fields. We discuss the opportunity and present the first results of new-type experiments on simulation of Jets with LPP at KI-1 facility of ILP, at moderate magnetic field ∼ kGs, oriented quasi-transverse (S ≍ 600) of LPP-blob expansion (with velocity V 0) relative to B 0. They were done on the base of all our preliminary studies, both at large-scale, high-vacuum chamber (0120 cm of KI-1) and others devices with LPP (oriented earlier at V0 transverse to B0, with $ = 900).