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Materials for Solar and Power Conversion Devices

Our interest in III-V materials include Gallium Nitride (GaN); Gallium Phosphide (GaP) and their alloys with other elements.  We are also interested in bulk crystals of GaN along with single crystal layers on homo- and hetero-substrates.

Halide Vapor Phase Epitaxy (HVPE) Facility: We have a custom built HVPE reactor consisting of a 48 inch long and 50mm ID quartz tube, with two heating zones for sources where the temperature can reach up to 1000 °C and is controlled by a furnace and one additional zone for deposition heated by induction. The setup also includes a bubbler for PCl3 with temperature control. Nitrogen and hydrogen can be fed interchangeably through two different channels.  This reactor is currently used for deposition of Gallium Phosphide (GaP) and related materials typically on 1-inch  Silicon wafers.

Metalorganic Chemical Vapor Deposition Facilities: The lab is also equipped with a hybrid reactor with gas delivery lines for Ga (TMG), In (TMI), Al (TMA) precursors for MOCVD along with 3 kW MW and ECR sources in two different chambers using a RF inductively coupled heater for substrate stage, and a substrate manipulator and bias. This reactor allows experiments on a variety of materials systems using controlled conditions of precursors, temperature and gentle plasmas using ECR and using a showerhead for several MOCVD precursors delivery into downstream chamber. This reactor will allow deposition onto 4-inch substrates and allows more control and flexibility for materials synthesis.


Electron Cyclotron Resonance (ECR) Plasma Enhanced Chemical Vapor Deposition Reactor: This reactor, which produces high density reactive plasmas, is equipped with an ECR plasma source (ASTeX ® Model AX4500), a 260W microwave power generator and a 25V/40A ECR power supply. The flow (up to 4 different gases) is automatically controlled. Two different substrate stages can be used with this reactor. One is stationary with a Boroelectric™ heater which can heat the substrate up to 1100°C, the other one, is a rotating (>2000 rpm) heating stage. This equipment is currently being used for the growth of bulk gallium nitride (GaN) via direct nitridation of Ga in the presence of nitrogen plasma. Additionally, the use of gentle hydrogen plasmas allows for reduction, etching and cleaning processes.


Radio Frequency (RF) Plasma Enhanced Chemical Deposition Reactor (RF-PECVD): This reactor is comprised of a 3ft x 22 mm ID quartz tube is fitted with a 1-zone tube furnace for external heating with automated temperature control up to 1100°C. Gas flow (up to 4 different gases) is also automatically controlled. Plasmas (0-600W) are produced by a RF generator (Seren R601) through an automatic matching network controller (Seren MC2). The applications of this reactor include: growth of silicon nanowires, fundamental studies of plasma-catalysis, gentle hydrogen plasma for reduction, etching and cleaning processes, and gentle nitrogen plasma for nitridation of materials.


Metal Oxides for Batteries and Catalysts

In the case of metal oxides, we have interests in a number of materials systems and in different formats – thin films, nanoparticles and nanowires. Most importantly, the composition and phase control and high throughput methods are of significant interest.


Atmospheric Plasma Discharges: Equipped with a microwave plasma flame for fast bulk production of nanowires. Also has a microwave system with upward flame with auto matcher for foil oxidation. In addition, there are two custom-built, atmospheric plasma jet reactors for bulk production of nanowires. A custom-designed/developed atmospheric microwave plasma jet reactor for bulk production of various metal oxide nanowire powders (gram qty).


Hot-filament Chemical Vapor Deposition (HFCVD): Custom-built HFCVD reactor (3ft x 40 mm ID quartz tube) equipped with resistively heated refractory metal sources (Mo, Nb, W, Ta). Reactor is fitted with a 1-zone tube furnace for external heating with automated temperature control up to 1400 C. This reactor is used for deposition of thin films and nanostructured layers of refractory metals, refractory metal oxides and nitrides with filament operating temperatures up to 2500ºC, at pressures between 30 mTorr – 100 Torr, in H2, N2, O2 and/or Ar atmospheres. In addition, this equipment can be used for pyrolysis, annealing, oxidation, reduction, and nitridation of materials.


Fluidized bed RF plasma reactor: UofL group designed and built equipment for bulk production and modification of nanowires: long tube, hot-filament reactor for uniform synthesis over large areas of quartz tubes and an inductively coupled RF plasma fluidized bed reactor for coating or functionalizing or synthesizing the nanomaterials.


Diamond and Related Materials for Thermionic Emission and Power Devices


We are interested in small crystal nucleation and large single crystal growth of diamond and with epitaxial film growth on hetero-substrates. n-type doping using phosphorous is of significant interest. The reactor facilities include ASTeX 5010 1.5 kW Microwave Chemical Vapor Deposition Reactor etc. Seki 5200: Multipurpose reactor with microwave and ECR plasma chambers with induction stage heater and stage manipulator. Capable of handling 4 inch wafers.


Microwave/ECR Plasma Enhanced Chemical Vapor Deposition Reactor, SEKI Technotron-ASTeX AX5200S-ECR: This reactor is equipped with a 3.0 kW microwave power generator that allow for high power density plasmas. In the same way, the reactor has an integrated ECR module to produce gentle plasmas. Substrate temperature (via an inductively coupled heater), chamber’s pressure and flows (up to 8 different gases) are automatically controlled. This reactor allows for the deposition of polycrystalline diamond films as well as the growth of single crystal diamond. Additionally, this reactor is used for reduction, etching and cleaning processes by using hydrogen, oxygen or hydrogen/oxygen plasmas.



Microwave Plasma Enhanced Chemical Vapor Deposition Reactor (MWPECVD), SEKI Technotron-ASTeX AX5010: This MWPECVD reactor is equipped with a 1.5 kW microwave power generator. Chamber’s pressure and gas flow (up to 4 different gases) are automatically controlled. Furthermore, this reactor is equipped with a doping system for phosphorous doping. This reactor allows for the deposition of doped and undoped polycrystalline diamond films. This reactor is also used for reduction, etching and cleaning processes by using hydrogen, oxygen or hydrogen/oxygen plasmas

CVD Reactor Accessories: Ocean Optics Spetrometer for Emission Spectroscopy, Infra-Red Optical Pyrometer, Dual Wavelength Williamson PRO 92-40-C Pyrometer for temperature measurements, Residual Gas Analyzer with SRA spectrometer (200 amu), and Heating (>900C), Rotating (>2000 rpm) Substrate Stage for ECR reactor.

Advanced Energy Materials


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