Influence of Ge nanocrystals and radiation defects on C-V characteristics in Si-MOS structures

Shai Levy, Issai Shlimak, Avraham Chelly, Zeev Zalevsky, Tiecheng Lu

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5 Scopus citations


Metal-oxide-semiconductor (MOS) structures containing 74Ge nanocrystals (NC-Ge) imbedded inside the SiO2 layer were studied for their capacitance characterization. Ge atoms were introduced by implantation of 74Ge+ ions with energy of 150 keV into relatively thick (∼640 nm) amorphous SiO2 films. The experimental characterization included room temperature measurements of capacitance-voltage (C-V) dependences at high frequencies (100 kHz and 1 MHz). Four groups of MOS structures have been studied: The 1st-"Initial" samples, without Ge atoms (before ion implantation). The 2nd-"implanted" samples, after Ge+ ion implantation but before annealing, with randomly distributed Ge atoms within the struggle layer. The 3rd-samples after formation of Ge nanocrystals by means of annealing at 800 °C ("NC-Ge" samples), and the 4th-"final" samples: NC-Ge samples that were subjected by an intensive neutron irradiation in a research nuclear reactor with the integral dose up to 1020 neutrons/cm2 followed by the annealing of radiation damage. It is shown that in "initial" samples, the C-V characteristics have a step-like form or "S-shape", which is typical for MOS structures in the case of high frequency. However, in "implanted" and "NC-Ge" samples, C-V characteristics have "U-shape" despite the high frequency operation. In addition, "NC-Ge" samples exhibit a large hysteresis which may indicate charge trapping at the NC-Ge. Combination of the "U-shape" and hysteresis characteristics allows us to suggest a novel 4-digits memory retention unit. "Final" samples indicate destruction of the observed peculiarities of C-V characteristics and recurrence to the C-V curve of "initial" samples.

Original languageEnglish
Pages (from-to)5189-5191
Number of pages3
JournalPhysica B: Condensed Matter
Issue number23-24
StatePublished - 15 Dec 2009


  • C-V characteristics
  • Isotopically enriched Ge nanocrystals
  • MOS structures
  • Neutron-transmutation doping


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