Solid State Communications, Vol. 60, No. 8, pp. 675-679, 1986. 0038-1098/86 $3.00 + .00 Printed in Great Britain. Pergamon Journals Ltd. ION SECONDARY ELECTRON EMISSION FROM A12Oa AND MgO FILMS N.R. Rajopadhye, V.A. Joglekar, V.N. Bhoraskar and S.V. Bhoraskar Department of Physics, University of Poona, Pune, 411 007, India (Received 17 September 1985 by C.W. McCombie) Coefficients of ion induced secondary electron emission (ISEE) 3' from thin films of A12Oa and MgO have been measured for argon ions in the energy range between 0-3 keV. Dionne's equation for secondary electron emission, which consists of production and emission terms has been modified to explain the kinetic emission of ISEE. The production term for ion induced secondary electrons has been separately formulated, taking account of the energy loss of primary ions, while the process of emission is considered to remain the same as in SEE. The escape depth Xs and emission probability B were obtained from the SEE data and were used, along the range value of incident ions, to calculate the emission term in ISEE. The modified form of the equation was used to evaluate theoretically expected ISEE yield energy curves. Fairly good correlation is observed in theoretical and experimental curves which supports the validity of the proposed theoretical model. 1. INTRODUCTION SECONDARY ELECTRON EMISSION (SEE) from a solid surface is of interest for its wide variety of applications. Although extensive work is reported on the electron induced secondary electron emission (SEE), little is reported in the field of ion induced secondary electron emission (ISEE). The ISEE itself plays an important role in ion-neutralization spectroscopy, ion induced Auger electron spectroscopy and also has applications in gas discharge panel displays [ 1] and in ion to electron convertors in mass spectrometers. Though ISEE yields for metals have been investigated in con- siderable detail [2-4] very meagre data [5-7] is available for insulating surfaces. Further, a satisfactory theory for kinetic emission in ion induced secondary electron emission is not developed, so far, which would include the physical parameters of solids; although Hagstrum [8] and Takeshi [7] have developed theories for potential emission. An attempt has been made here to formulate a theory for ISEE yield which is basically modified from the Dionne's equation for SEE [9]. Dionne's theory assumes that the SEE mechanism consists of two con- secutive and independent processes-production and emission. Since ion impact will affect only the pro- duction term (P), a modification is required to include the energy loss of primary ions, whereas the emission term (S) remains unaffected. In Dionne's equation [9] 'P' includes the parameters like ionization potential, stopping power of primary electrons and range of primary electrons while 'S' is accounted by the escape depth X8 and emission probability B. The parameters Xs and B were estimated from the SEE measurements for the same sample. The production term in ISEE is how- ever expressed separately making use of stopping powers and range energy relation for a solid corresponding to the incident ions. Finally a theoretical model is proposed and it has been shown to give a fairly acceptable agree- ment between the experimental and theoretical data. The paper reports the measurements of coefficients of SEE (5) and ISEE (3') for thin films of A1203 and MgO. A single-pulse method incorporated with LEED/ Auger geometry in an UHV system was used for measuring the SEE yields. Simultaneous work function measurements were also recorded by a retarding potential technique using a low energy electron gun. Samples were then transferred to a mass spectrometer system for the ISEE yield measurements. Very low primary current (~ 10 -12 A) of Ar + ions was used to avoid the surface charging. 2. EXPERIMENTAL 2.1 Sample preparation The MOCVD technique [10] was employed tG deposit AI2Oa films whereas MgO films were deposited by electron beam evaporation method. The thickness of the films was about 200 A and they were deposited on a semiconducting SnO2 coating which assists in charge neutralisation. 2. 2 1SEE measurements The experimental arrangement is shown in Fig. 1. 675