Nano-imaging mass spectrometry by means of high-energy laser desorption ionization (HELDI)

Reduction of a sampled mass at the nano-scale degrades the sensitivity. Therefore, a theoretical analysis was carried out to assess the sample utilization efficiency, and the leeway for the enhancement of the sensitivity. High (photon)-energy laser desorption ionization (HELDI) is a novel microanalytical technique that uses XUV laser pulses to enhance and homogenize the sensitivity at the nano-scale, especially for light elements. While inspecting nanostructures in 3D, local heterogeneities are critical and are spotted only if the instrumental variance can be discerned from the compositional one. Such underlying information was found to be accessible when studying the data scatter distribution. Such an analytical method was applied to analyze functional thin films of photovoltaic kesterite materials, probed with HELDI hyphenated to time-of-flight mass spectrometry. The results indicated an enhanced analytical capability for imaging light elements and the ability to discern instrumental variances (random errors) from true compositional ones (heterogeneity). A calibration curve is built on points spread over a range, which is a function of the variance of the blank, instrumental error and heterogeneity.