Czochralski grown single crystalline silicon, Cz-Si, contains oxygen admixture, in a concentration up to about 0.004 %, typically in the form of interstitials, Oi. At annealing Oi's are gathering creating oxygen and silicon containing clusters with increasing (with annealing temperature) dimensions. In particular, annealing of Cz-Si at about 720 K results in producing of the oxygen-silicon nanoclusters exhibiting electrical activity (thermal donors, TDs ).
Thermoelectric properties of Cz-Si with different concentrations of TDs were investigated in this work at quasi-hydrostatic pressures (HP) up to 16 GPa. The Cz-Si samples were cut from the (001) oriented Cz-Si wafers sujected to prolonged pre-annealing (up to 40 h) under atmospheric pressure to create TDs, as determined by infrared (FTIR) and electrical measurements.
Thermopower of TDs-containing Cz-Si was measured in the pressure apparatus with anvils from synthetic diamond and hard alloy . The X-Ray emission spectra were determined using the ultrasoft spectrometer; some microhardness characteristics of TDs-containing Cz-Si were also determined.
Calculation of the electronic structure of investigated samples was performed in the Local Spin Density approximation. Among others it has been stated that:
- the absolute value of thermoelectric power is depentent on the TDs concentration; it decreases with HP up to HP = 7-10 GPa, at which pressures the transition to the metallic phase takes place; - the transition pressure as well as other HP - related characteristics of the Cz-Si samples are dependent on the TDs concentration. It has been proven that the thermoelectric power measured under HP is highly sensitive to the changed concentration of oxygen nanoclusters (TDs) and of other microdefects.
The work was supported by RFBR 01-02-17203.
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