EFFECT OF AN EXTERNAL ELECTRIC-FIELD ON CHARGE-TRANSFER AT A FUNCTIONAL MONOLAYER N-SI(111) INTERFACE/

The functional organic monolayer/n-Si(111) assembly was fabricated for an investigation of photoelectric memory effect by the Langmuir-Blodg ett technique from 2-carboxyethyl)-4-[4'-N,N-(dioctadecylamino)stryl] pyridium (P-I). The measurement of the surface photovoltage spectra (S PS) of this assembly shows that it has an erasable photoelectric memor y effect: after a voltage of 20 V was applied to this assembly upon ir radiation with visible light, the surface photovoltage (SPV) of this a ssembly becomes stronger, the increase of SPV can remain; followed by the application of a voltage of -20 V in the dark the SPV can return t o the initial value (i.e. the value without being treated with an exte rnal field). Based on the principle of surface photovoltage spectrosco py, it is suggested that the electron acceptor 2-carboxyethyl pyridium in the hydrophilic head of P-I can capture the photogenerated electro n from the conduction band of n-Si(lll) as an electron trap upon irrad iation with visible light under the help of a positive external electr ic field, and the trapped electron can return to the conduction band o f n-Si(111) on the application of a negative external electric field.