Composition and crystallography dependence of the work function: Experiment and calculations of Pt-Al alloys

Abstract

The work function (WF) of several phases of Pt-Al alloys is investigated. A first-principles study is performed to determine the dependence of the vacuum WF (VWF) on the phase, crystallographic orientation, and atomic termination. In parallel, the effective WF (EWF) of these alloys is experimentally measured using metal-oxide semiconductor devices. A detailed microstructural characterization based on x-ray diffraction and transmission electron microscopy allows the comparison between experiment and calculations. It is found that despite the formation of a complex microstructure, the calculated VWF values are in good agreement with the experimental EWF values. The possible VWF range for each phase has a relatively small (∼0.5 eV) span for different orientations and atomic terminations, and it is found that Pt atoms in the terminating plane are more dominant than Al atoms. The results demonstrate that first-principles calculations of the WF of alloys can be used to successfully predict the experimental WF and that knowledge of the microstructure is important for the accuracy of these calculations.

The electrostatics of Ta2O5 in Si-based metal oxide semiconductor devices

“…This means that the only electrostatic contribution of Ta 2 O 5 at the Al 2 O 3 -SiO 2 interface is by creating a separation between Al 2 O 3 and SiO 2 . Indeed, it is known that an Al 2 O 3 -SiO 2 contact increases the EWF (and V FB ), and we have previously reported an increase of 0.4 eV, 12,22,42 in agreement with other reports of 0.2 $ 0.7 eV. 20,43-45 By contrast, in the current work, the contribution of the Al 2 O 3 -SiO 2 interface is 1 6 0.2 eV (Fig.…”

“…The principal difference between the current work and the literature is the larger EOT between the Al 2 O 3 -SiO 2 interface and the top metal, which is $4 nm in the current work versus $2 nm in previous reports. 22,42 According to the Poisson equation, 41 the potential shift caused by Al 2 O 3 -SiO 2 interface charges will have a distance (between the metal and the Al 2 O 3 -SiO 2 interface) dependence. If this V FB shift indeed depends on the EOT of the Al 2 O 3 layer, it could imply that charges at the Al 2 O 3 -SiO 2 interface may play a role in the shift, as argued before.…”

Theoretical studies of the work functions of Pd-based bimetallic surfaces

“…Additional dipole moment can be formed by electron rearrangement triggered by adsorption or surface doping and then shifts the work function. [14][15][16] In general, the variation of the work function can be mainly determined by the direction and extent of electronic charge transfer, and electron transfer from the substrate to the surface species usually leads to an increase of the work function. 17 It makes measuring the shift of the work function useful to characterize electron transfer induced by molecular adsorption.…”

Error estimates for density-functional theory predictions of surface energy and work function

“…The usefulness of DFT simulations therefore depends on their accuracy, i.e., the deviation with respect to experimental results. A number of studies have attempted to assess the accuracy of DFT-predicted surface properties [7][8][9][10][11][12][13][14][15][16][17][18]. Most of these studies, however, only consider a limited set of test surfaces, which brings into question the transferability and statistical significance of the accuracy estimate.…”