Indirect electron beam induced ferroelectric domain breakdown

3 Indirect electron beam induced ferroelectric domain breakdown 

Calculations of the incident electron penetration depth into the dielectric layer is a well understood phenomenon [58,59] in recent years many Monte Carlo simulation tools were developed to study it. In our case it allowed an easy calculation of the photoresist layer thickness for different exposure parameters of the eb. For example if the eb exposure is done with Vo = 15 kV accelerating voltage and the dielectric layer is selected to be polymethylmethacrylate (pmma), we estimate the penetration depth by Kanaya and Okayama s [58] expression  

Where Vo is the accelerating voltage in kV, A is the average atomic weight in g/mol, p is the density in g/cm3 and Z is the average atomic number. For pmma having the parameters 

10 Ferroelectric Domain Breakdown Application to Nanodomain Technology 

It can be seen that most of the electrons are localized in the 3.5 pm thick layer and only a few of them penetrate to a depth of 3.8 pm. In our experiments a 0.5 mm thick LiNbC 3 crystal was spin-coated with 3.5 pm thick photoresist layer (Shipley 1818). The prepared sandwiched structure was exposed using a commercial eb lithography system (elphy Plus) adapted to a jeol jsm 6400 scanning electron microscope on the C -face of the LiNb03 sample under various accelerating voltages and surface charge densities, as shown in Table 10.1. 

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