Experiments

• CCPs are simple, low impurity plasmas commonly used for processing. EEDF influences the rate of reactions and collisions, impacting species generation and processing parameters
• EEDF varies over the course of one RF cycle (74 ns period in 13.56 MHz supply)
• ns resolution time resolved Langmuir probe used to measure electron density and EEDF throughout the RF cycle.

This work uses a time-resolved Langmuir probe to measure the electron energy distribution function (EEDF) in a capacitively-coupled parallel-plate (CCP) plasma reactor. The EEDF completely determines the plasma chemistry in a low-temperature plasma, and that is why it is so important to obtain. By seeing how the EEDF changes throughout an RF cycle, both as a function of time and position, one then knows the extent by which altering the RF waveform can affect the energy of the electrons. Often industry mixes RF frequencies to alter the plasma — particularly the ion energy distribution at the substrate. Here we add a second frequency in a systematic manner and examine the changes in the instantaneous EEDF. We also examine the turn on and turn off times of the RF generator itself. Specialized circuits were designed for this work to ensure high frequency fidelity so digitization at 1.5 GHz is possible and accurate. A set of experiments were conducted to show how only altering circuit parameters affect the results, and steps were taken to eliminate those effects. Spatial variations of the resulting EEDFs were investigated, especially near the edge of the CCP reactor, to see which aspects change the most with radius.

Graphene is a 2D carbon structure with many useful properties including strength, conductivity, flexibility, and more. At IPI, graphene is grown in atmospheric pressure plasmas, breaking down methane (CH₄), allowing the carbon radicals to recombine in a graphene-like structure.

Graphene is utilized in various applications, including battery technology and composite materials. Typical lithium-ion batteries can be altered to include graphene, which can improve battery life, increase the number of recharge cycles, improve conductivity, and even decrease the weight of the batteries. Because of the difficulty of growing graphene, understanding the growth mechanisms is vital to improving the conditions of the reactors, allowing for greater production rates and more graphene-like material, as opposed to amorphous carbon or carbon black. With an increase in graphene production and quality comes more efficient technologies, stronger materials, and increased battery life.

Liquid lithium has been considered as a plasma facing component (PFC) as it can provide access to low recycling regimes due to its gettering abilities. However, in a low recycling regime, lithium is not only collecting impurity species, but also tritium. It is necessary to recover this tritium due to inventory and cost constraints. The purpose of Flowing Lithium’s Adsorption and Release Experiment for Deuterium (FLARED) is to investigate the uptake and transport of hydrogenic species.

The FLARED project adds an ECR plasma source to the Actively Pumped Open-surface Lithium Loop (APOLLO). This source will generate a Deuterium plasma, creating a flux of deuterium ions and radicals to the flowing liquid lithium Plasma Facing Component (PFC) installed in APOLLO. Through an array of plasma and neutral diagnostics and careful characterization the uptake of deuterium into the lithium can be measured. The Hydrogen Desorption Experiment (HyDE) distillation column will be installed downstream of the lithium PFC. This will allow for thermal treatments of deuterated lithium to separate the deuterium from the lithium. A differentially pumped RGA will be installed at the top of the column to measure the recapture rate of deuterium allowing for a balance of the ‘fuel’ within the system to be determined.  This work is sponsored by Tokomak Energy inc.

SHADE has two 4-inch PVD sputtering guns, a load-lock and a rotating sample stage.  It is also outfitted with detailed diagnostics to enable time-resolved measurements of HIPIMS discharges.  It is powered by a Starfire Industries IMPULSE that is capable of cathode-voltage reversal.  It has been used to make multi-layer mirrors, and do reactive sputtering experiments.

The company COMET makes advanced RF power supplies capable of fast-turn on and matching.   We will be using one of their supplies in an ICP configuration and measuring the time-resolved plasma conditions to correlate the to the settings of the power supply.

This is a PVD sputtering tool manufactured by the Material Research Corporation (MRC).  It uses a 14 inch diameter target and a rotating magnet pack.   We have outfitted it with a variety of HIPIMS power supplies, used a variety of magnet packs, diagnostics and internal ionization coils.

ECAP is a microwave-powered atmospheric-pressure plasma torch.  It has three zones where reactants can be introduced to the plasma.  In this way it can make a variety of coatings, which would normally require a vacuum system to produce.

When a femtosecond laser pulse hits a surface, the power is incredible.  It is so intense that it instantly turns the surface into a plasma even before the laser pulse ends.  This means there is a chance that the laser light is converted to surface plasmons, and they will deposit their energy as a constructively interfered wave.  This leads to ripples on the surface with dimensions near the wavelength of the initial laser.   This texturing can be used for photonic properties, or to alter the wetting of the surface.  We learned that such ripples can prevent wetting of metal surfaces by lithium.

XCEED is an XTS-13-35 EUV source made by Xtreme Technologies.  The same model source was used to make the very first chips that used EUV lithography in INTEL’s MET tool.  It uses a discharge-produced plasma from a Z-pinch and puts 5 J of energy into the plasma in 5ns.    This device will be re-purposed to study warm-dense matter in a project funded by Los Alamos National Laboratory.

The Mock Entry Module for East (MEME), a 1.2m x 1.2m x 1.2m vacuum system, is a replica of the energy module for the EAST tokamak in China and is used for molten lithium experiments and diagnostic development.