Persistent photoconductivity at elevated temperatures

Persistent photoconductivity measurements have been made on several samples of (Formula presented) with manganese concentrations in the range 5-15 %. The effect of composition on the persistent photoconductivity (PPC) effect has been studied. The PPC is usually quenched at a temperature of about 100 K but some samples exhibit PPC which exists up to 190 K. The origin of this effect is discussed in terms of several models of PPC. Particular attention is paid to the various possibilities for multiple (Formula presented)-like centers in these materials. Also, a small number of samples have been identified as being possible candidates for being driven through the insulator-metal transition via photodoping. One possible application of these samples (which has already been suggested) would be to write erasable conductive, or even metallic, patterns on an insulating background. The requirements for this area of application are discussed in order to ascertain whether (Formula presented) is a suitable material.