Spectral Sensitivities of X-Ray Diffraction and Atomic Force Microscopy to the Roughness of Si/SiO 2 Interfaces

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=

Iamnexp(-i(mqox+nqoy+onmn), with q0o

The roughness

=

m,n

spectrum is given by: W(kx,ky)

=

IZ(k,k y)12

L

L

-L

-L

2

(ekxx+k Y)dxdy()

L

2

2

lIamn 12 (kx-mq0) 8(ky -nq0)

= m,n

We note that W(kx ,ky) is the Fourier transform of the height-height correlation function. 2 The root mean square is defined as = /< (z-) >. We define h(x,y) = z(x,y)- such that = 0, and so h (x, y) = amn exp (- i (mq0 x + nq0 y+ mn )-a00 Using our expression for z, we 2m,n

2XY>=1,

have a2 = L, no information is lost due to IL' To provide some intuition we illustrate this in one dimension. The finite Fourier transform L'

2

Z(k)

f z(x)eikxdx

=

(2)

-L1 2

can Z

be x=

written

in

reciprocal

space

as Z(k) = Z_, (k) *coh(k) where kL' sin(-) The convolution of Z,,(k) 2

j z(x)eikxdx, and coh(k)

2 with coh(k) implies that fluctuations with wave-vectors Aq