This work investigates how knock-on displacements influence fluctuation electron microscopy (FEM) experiments. FEM experiments were conducted on amorphous silicon, formed by self-ion implantation, in a transmission electron microscope at 300 kV and 60 kV at various electron doses, two different binnings and with two different cameras, a CCD and a CMOS one. Furthermore, energy filtering has been utilized in one case. Energy filtering greatly enhances the FEM data by removing the inelastic background intensity, leading to an improved speckle contrast. The CMOS camera yields a slightly larger normalized variance than the CCD at an identical electron dose and appears more prone to noise at low electron counts. Beam-induced atomic displacements affect the 300 kV FEM data, leading to a continuous suppression of the normalized variance with increasing electron dose. Such displacements are considerably reduced for 60 kV experiments since the primary electron's maximum energy transfer to an atom is less than the displacement threshold energy of amorphous silicon. The results show that the variance suppression due to knock-on displacements can be controlled in two ways: Either by minimizing the electron dose to the sample or by conducting the experiment at a lower acceleration voltage.

High-resolution radial distribution functions of as-implanted and thermally relaxed amorphous silicon created by ion implantation were measured using tilted-illumination selected area electron diffraction at room temperature. The diffracted intensities were measured out to a maximum scattering vector 2 sin(θ)/λ of 3.3–3.7 Å−1. The volume-averaged pair-correlation statistics of as-implanted and relaxed ion-implanted amorphous silicon are virtually indistinguishable with coordination numbers of 3.7 ± 0.3 and 3.9 ± 0.3 (for neighbors closer than 3 Å) and average bond angles of 109 ± 0.5° and 110 ± 0.6°, respectively. The atomic rearrangements in ion-implanted amorphous silicon due to a low temperature anneal are subtle.

We examine simulated electron microdiffraction patterns from models of thin polycrystalline silicon. The models are made by a Voronoi tessellation of random points in a box. The Voronoi domains are randomly selected to contain either a randomly-oriented cubic crystalline grain or a region of continuous random network material. The microdiffraction simulations from coherent probes of different widths are computed at the ideal kinematical limit, ignoring inelastic and multiple scattering. By examining the normalized intensity variance that is obtained in fluctuation electron microscopy experiments, we confirm that intensity fluctuations increase monotonically with the percentage of crystalline grains in the material. However, anomalously high variance is observed for models that have 100% crystalline grains with no imperfections. We confirm that the reduced normalized variance, V(k,R) − 1, that is associated with four-body correlations at scattering vector k, varies inversely with specimen thickness. Further, for probe sizes R larger than the mean grain size, we confirm that the reduced normalized variance obeys the predicted form given by Gibson et al. [Ultramicroscopy, 83, 169–178 (2000)] for the kinematical coherent scattering limit.

Solid phase crystallization of plasma-enhanced chemical-vapor-deposited (PECVD) amorphous silicon (α-Si:H) in α-Si:H/Al and Al/α-Si:H structures has been investigated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Radiative heating has been used to anneal films deposited on carbon-coated nickel (Ni) grids at temperatures between 200 and 400°C for TEM studies. α-Si:H films were deposited on c-Si substrates using high vacuum (HV) PECVD for the XRD studies. TEM studies show that crystallization of α-Si:H occurs at 200°C when Al film is deposited on top of the α-Si:H film. Similar behavior was observed in the XRD studies. In the case of α-Si:H deposited on top of Al films, the crystallization could not be observed at 400°C by TEM and even up to 500°C as seen by XRD.