Experimental low-voltage-point projection microscopy

The paper presents an atomic resolution achieved by low voltage point projection microscopy. Since resolution is approximately equal to virtual source size, it demonstrates field-emission from tip regions of atomic dimensions. Ray-tracing calculations show the aberration coefficients and size of the virtual source to be sub nanometer. The brightness of such a nanotip has been measured to be 7.7 × 10 ¹⁰ A cm ^-2 sr ^-1 (at 100kV). The images require the theory of LEED for interpretation and are always out of focus by the tip to sample distance z1. The instruments hold promise for imaging small organic molecules (across holey carbon grid), LB and other thin organic films where radiation damage is dominated by inner-shell processes.