Browsing by Subject "CDTE"

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  • Gädda, Akiko; Ott, Jennifer; Karadzhinova-Ferrer, Aneliya; Golovleva, Maria; Kalliokoski, Matti; Winkler, Alexander; Luukka, Panja; Härkönen, Jaakko (2019)
    The suitability of two low-temperature dielectric passivation layer processes for the fabrication of Cadmium Telluride (CdTe) X-ray detectors has been investigated. The CdTe crystals with a size of (10 10 1) mm were coated with sputtered aluminum nitride (AlN) or with aluminum oxide (AlO) grown by the atomic layer deposition (ALD) method. The metallization contacts of the detectors were made by titanium tungsten (TiW) and gold (Au) metal sputtering depositions. The pad detector structures were patterned with proximity-contactless photolithography techniques followed by lift-off patterning of the electrodes. The detector properties were characterized at room temperature by Transient Current Technique (TCT) measurements. The obtained results were compared and verified by numerical TCAD simulations of the detector response. Our results indicate that higher signal charge was collected from samples with AlO. Furthermore, no significant laser light induced signal decay by CdTe material polarization was observed within order of 30 min of continuous illumination.
  • Brücken, Erik; Bharthuar, Shudhashil; Emzir, M.; Golovleva, Maria; Gädda, Akiko; Hostettler, R.; Härkönen, J.; Kirschenmann, Stefanie; Litichevskyi, Vladyslav; Luukka, Panja; Martikainen, Laura; Naaranoja, Tiina; Nincâ, Ilona Stefana; Ott, Jennifer; Petrow, H.; Purisha, Zenith; Siiskonen, Teemu; Särkkä, Simo; Tikkanen, Joonas Samuli; Tuuva, Tuure; Winkler, Alexander (2020)
    We present the current status of our project of developing a photon counting detector for medical imaging. An example motivation lays in producing a monitoring and dosimetry device for boron neutron capture therapy, currently not commercially available. Our approach combines in-house developed detectors based on cadmium telluride or thick silicon with readout chip technology developed for particle physics experiments at CERN. Here we describe the manufacturing process of our sensors as well as the processing steps for the assembly of first prototypes. The prototypes use currently the PSI46digV2.1-r readout chip. The accompanying readout electronics chain that was used for first measurements will also be discussed. Finally we present an advanced algorithm developed by us for image reconstruction using such photon counting detectors with focus on boron neutron capture therapy. This work is conducted within a consortium of Finnish research groups from Helsinki Institute of Physics, Aalto University, Lappeenranta-Lahti University of Technology LUT and Radiation and Nuclear Safety Authority (STUK) under the RADDESS program of Academy of Finland.