Effect of matrix composition and impact angle on the fractional ion yield of Be+sputtered from oxygenhyphen;bombarded silicon and compound semiconductors

摘要

Using two different secondary ion mass spectrometers we have determined fractional ion yields of Be+sputtered from seven berylliumhyphen;implanted semiconductor matrices (Si, GaAs, AlxGa1minus;x, InGaAs, and InP) by O+2bombardment. The measurements were performed at five different impact angles thgr; ranging from nearhyphen;normal beam incidence, i.e., thgr;=2deg;, to thgr;=42deg;. The fractional yields dgr;Y+Beshow a strong matrix dependent variation (up to a factor of more than 100) as well as a pronounced thgr; dependence. Even though the two instruments differ considerably with respect to the geometry and the strength of the secondary ion extraction field, the matrixhyphen;dependent variations in dgr;Y+Bewere almost the same for the same thgr;. On the basis of these findings previously reported discrepancies in the magnitude of the Be matrix effect can be attributed almost completely to the thgr; dependence of the ionization probability. Moreover, it is shown that a universal relationship between the ion yield dgr;Y+and the matrix sputtering yieldYcannot be established because of functional dependence dgr;Y+(Y,thgr;) is different for each impact angle. Further evidence in this respect is obtained from theYdependence of the ionization probability of Be+, derived by roughly correcting the measured fractional ion yields for thgr;hyphen;dependent variations in transmission of the employed quadrupole based instrument. A firsthyphen;order correction to the Be+matrix effect can be obtained from the O+intensity measured quasisimultaneously with the Be+intensity.