Patent Document ID: 9182363
Application ID: 14079968
Patent Flag: 1

Claim One:
1. A method of measuring an areal concentration of a target element coated by more than one layers near the surface of a substrate, the target element capable of emitting La, LI3 and L7 x-rays when suitably excited, the method comprising the steps of: a) inducing the L α and L β and L γ x-rays to be emitted from said target element with excitation radiation; b) detecting said L α , L β and L γ x-rays and determining the intensity of the L α , L β and L γ x-rays separately; c) calculating the areal concentration of said target element by means of the following equations: 
 m 1 =I Lβ /A 1/ I LβS Eq. 1 wherein m 1 is the calculated lead concentration based on single layer model using L α and L β intensities; A1 is the absorption factor computed from the L α , L β intensity ratio, wherein during calibration, A1 as a function of L α , L β intensity ratio is fitted as a curve; and this curve is used later to calculate the A1 from measured L α ,L β intensity ratio; I Lβ is the measured L β line intensity of the target element from sample under testing; I LβS is the L β intensity of the target element from a NIST standard without any shielding layers; 
 m 2 =I Lγ /A 2/ I LγS Eq. 2 wherein m 2 is the calculated lead concentration based on single layer model using L β and L γ intensities; A2 is the absorption factor computed from the L β , L γ intensity ratio, wherein during calibration, A2 as a function of L β , L γ intensity ratio is fitted as a curve; and this curve is used later to calculate the A1 from measured L α , L β intensity ratio; I Lγ is the measured L γ line intensity of the target element from sample under testing; I LγS is the L γ intensity of the target element from a NIST standard without any shielding layers; and d) calculating the combine areal concentration of said target element according to: 
 m z =m 2 +C 3 ( m 2 −m 1 )  Eq. 5 wherein C 3 is a constant determined during an instrument calibration, and m z is the target element concentration emitted from the at least one layer of coating containing the target element.