In-situ Measurement of Self-Atom Diffusion in Solids Using Amorphous Germanium as a Model System

Abstract

We present in-situ self-diffusion experiments in solids, which were carried out by Focussing Neutron Reflectometry on isotope multilayers. This new approach offers the following advantages in comparison to classical ex-situ measurements: (1) Identification and continuous measurement of a time dependence of diffusivities, (2) significant reduction of error limits of diffusivities, and (3) substantial reduction of the necessary experimental time. In the framework of a case study, yet unknown self-diffusivities in amorphous germanium are measured at various temperatures quasi-continuously, each during isothermal annealing. A significant decrease of diffusivities as a function of annealing time by one order of magnitude is detected that is attributed to structural relaxation accompanied by defect annihilation. In metastable equilibrium the diffusivities follow the Arrhenius law between 375 and 412 °C with an activation energy of Q = (2.11 ± 0.12) eV. The diffusivities are five orders of magnitude higher than in germanium single crystals at 400 °C, mainly due to the lower activation energy.

Модификация структурно-морфологических свойств германия в многослойной нанопериодической структуре Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-/Ge с промежуточными слоями Si при отжиге

“…Малое содержание Si в кристаллитах может объясняться соотношением кинетики диффузии Ge-Si и происходящей одновременно кристаллизацией. Диффузия Si из аморфной фазы в сформированный кристаллит представляется существенно замедленной по сравнению с диффузией в аморфной среде, о чем можно судить по коэффициентам самодиффузии в аморфных Ge [30] и Si [31], которые оказываются на 5 порядков больше, чем в кристаллических.…”

Analysis of the Diffusion in a Multilayer Structure under a Constant Heating Rate: The Calculation of Activation Energy from the In Situ Neutron Reflectometry Measurement

“…In nonoxide high-temperature superhard ceramic coatings, nitrogen self-diffusion was measured in amorphous Si 3 N 4 , and in silicon carbo-nitrides. , For crystalline metal oxides, lithium self-diffusion was examined in LiNbO 3 . , Self-diffusion was measured in metals such as in nanocrystalline copper, iron, , and Fe-based compounds . In semiconductors, self-diffusion was measured in crystalline silicon , and germanium and in amorphous silicon and germanium . Extrinsic diffusion (so-called “Fremddiffusion”) was also suitably measured with NR − for lithium permeation through amorphous silicon, − amorphous lithium silicide, and nanocrystalline chromium thin layers.…”

“…The multi-isothermal annealing for the determination of the activation energy of atomic motion is timeconsuming and can last more than several hours. 49 To substantially reduce the time needed in the measurement of the temperature dependence of atomic diffusion, Huger et al 55 introduced the concept of increasing temperature at a constant rate in-situ NR measurements for the determination of the temperature dependence of atomic diffusion in solids. They have demonstrated the feasibility of this method in the study of atomic diffusion in amorphous 73 Ge/ nat Ge multilayers.…”

Neutron reflectometry to measure in situ the rate determining step of lithium ion transport through thin silicon layers and interfaces

“…NR permits the detection of buried interfaces deep within complex sample environments in a non-destructive manner and allows the study of in-operando processes in LIBs during device operation. [30][31][32][33][34][35][36][37][38] This work describes the use of neutron reflectometry to measure the transport of Li across Si layers in a multilayer. It is the latest in a series of related articles 26,29,35,[39][40][41] of increasing sophistication and quality of information.…”