Finite size effects: deuterium diffusion in nm thick vanadium layers

Abstract

We investigate the effect of finite size on the chemical diffusion of deuterium in extremely thin V(001) layers. A five fold increase in the diffusion coefficient is observed at concentrations around 0.2 [D/V], when the thickness of the V is decreased from 28 to 14 atomic layers (≈2.1-4.2 nm). The size dependent deuterium-deuterium interaction energy is argued to be the root of the observed changes as the diffusion rates are similar at low concentrations. The results demonstrate the feasibility of using finite-size effects to enhance the chemical diffusion of light interstitials in solids. We discuss the general applicability of these effects to other systems.

An Innovative Procedure to Evaluate the Hydrogen Diffusion Coefficient in Metals from Absorption Measurements

“…More recent techniques also relies on the use of light transmission to monitor the concentration of hydrogen as a function of both the position and time [15][16][17]. Another route to assess the diffusion coefficient is by performing permeation experiments.…”

The root cause of hydrogen induced changes in optical transmission of vanadium

“…Knowledge of the pressure-composition-isotherms of metal hydrides is crucial when studying for example hydrogen storage in metals, hydrogen embrittlement, and thin film hydrogen sensing applications [1][2][3]. Knowledge of the concentration and its distribution in a film can also be used to measure dynamic properties of hydrogen [4,5] and learn how these can change in the presence of finitesize [6]. In the case of thin films, optical transmission has been used to measure concentration for about two decades [1,2,4,5,[7][8][9][10].…”

Combined Light and Electron Scattering for Exploring Proximity Effects on Hydrogen Absorption in Vanadium

“…The chamber has two quartz windows and is heated externally. Light transmission is used to detect the hydrogen content [14], which can be converted from optical transmission using c = α ln(I c /I 0 ), where I c is the light transmission after hydrogenation while I 0 is the light transmission before hydrogenation; α is the absorption coefficient that is calibrated through comparing the neutron characterization to light transmission on the same sample [17]. A thermocouple is connected to the sample holder inside the chamber and is used to measure the sample temperature.…”