14-17 May 2019
US/Mountain timezone
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Purification of Ge ingots for growing crystals in developing dark matter detectors
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Content: High-purity germanium (HPGe) single crystal having the net impurity level of ~10^9 to 10^10 cm^-3 can be used for the fabrication of high-resolution Dark matter detectors. We implement Zone refining technique as a primary purification procedure for growing crystals. The raw germanium ingots in our laboratory have four main impurities, such as Aluminum (Al), Boron (B), Phosphorous (P) and Gallium (Ga), isolated to different parts of the ingot, which have been identified through photothermal ionization spectroscopy (PTIS), with net impurity level of (10^13-10^14) cm^-3. In order to setup zone refine germanium crystals, it is very important to take care of cleaning and etching procedure, additionally vacuum levels and the correct combination of ambient gases. The process of zone-refining included two-step strategy, which included initial purification of the raw germanium ingots in graphite boat, and then further purification of the zone-refined ingots from the first step in the carbon-coated quartz boat. We have optimized the parameter, zone length, zone travel speed and the number of passes for impurities ingots having distinguished segregation coefficient. Using the Van der Pauw Hall method, we were able to measure the electrical properties of zone refined ingots and analyze the distribution of impurities. Results obtained from Graphite boat Ingots have the impurity level of (10^11-10^12) cm^-3 and from Quartz boat Ingots (10^10-10^11) cm^-3. This work is supported by NSF OISE-1743790 and NSF PHY-1902577.
Id: 30
Room: EEP 253, Electrical Engineering & Physics Building
Starting date:
15-May-2019   16:40 (US/Mountain)
Duration: 20'
Contribution type: Oral Presentation
Primary Authors: ACHARYA, Pramod (University of south dakota)
Co-Authors: Prof. MEI, Dongming (The University of South Dakota)
PANTH, Rajendra (University of South Dakota)
KOOI, Kyler (University of South Dakota)
KIRKVOLD, Alex (University of South Dakota)
LI, Yangyang (University of South Dakota)
Presenters: ACHARYA, Pramod
Material: slide Slides
Included in session: Materials Science
Included in track: Materials Science for Nuclear and Particle Physics