1.         (a)     Giving full justification, suggest the best technique (or combination of

techniques) and experimental strategy that could be used to investigate each of the following situations (i) to (iii):

[Do not describe all the details of how the methods work from your notes.

Instead you should focus on the key features of the experiment that make it suitable for the situation and explain why other methods maybe less suited.]

(i)   the nature of lattice defects in a crystal of barium phosphate; (2 marks)

(ii)  the magnetic structure of Y3Fe5O12 ;  (3 marks)

(iii) accurate details of the structural packing arrangement in a crystal of benzoic acid and whether this structure is representative of the bulk sample. (4 marks)

(b)    Explain why, following exposure to gaseous carbon monoxide, the LEED

pattern for the (100) face of a single crystal of palladium remained the same, whereas the XPS spectrum of this surface contained additional peaks. (3 marks)

(c)    Both XRF and XPS maybe used to gain insights into the composition of a solid. Describe, giving an explanation of the underlying reasons, the extent to which these techniques probe the bulk composition versus the surface composition of the solid.  (4 marks)

2.         (a)     In a first experiment, the tip of a STM operated in constant height mode is

moved in direction x across the surface schematically depicted in Figure 1, where materials A and B are two metals with work functions ΦA and ΦB, respectively.

Sketch the dependence of the tunnelling current, I, on the lateral position,x, if

(i) ΦA  > ΦB

(ii)  ΦA  = ΦB