PLD plasma plume analysis: a summary of the PSI contribution

Abstract

We report on the properties of laser-induced plasma plumes generated by ns pulsed excimer lasers as used for pulsed laser deposition to prepare thin oxide films. A focus is on the time and spatial evolution of chemical species in the plasma plume as well as the mechanisms related to the plume expansion. The overall dynamics of such a plume is governed by the species composition in particular if three or more elements are involved. We studied the temporal evolution of the plume, the composition of the chemical species in the plasma, as well as their electric charge. In particular, ionized species can have an important influence on film growth. Likewise, the different oxygen sources contributing to the overall oxygen content of an oxide film are presented and discussed. Important for the growth of oxide thin films is the compositional transfer of light element such as oxygen or Li. We will show and discuss how to monitor these light elements using plasma spectroscopy and plasma imaging and outline some consequences of our experimental results.

Controlling the Polarization in Ferroelectric PZT Films via the Epitaxial Growth Conditions

“…[ 10 ] Note that in addition Pb excess at the surface can also be attributed to the PLD process itself, as light or volatile elements, such as Pb, get enriched in the plasma plume with longer growth duration. [ 32 ] As schematically shown in Figure 3a and previously evidenced, [ 10,14 ] the positively charged Pb‐excess region near the surface, as a result of the Pb concentration gradient, promotes a downward‐oriented polarization, opposite to the polarization direction imposed by the buffer layer. This competition reduces the net polarization and causes the ISHG signal to drop upon stopping the growth (Figures 1a and 2a).…”

Influence of Deposition Conditions and Thermal Treatments on Morphological and Chemical Characteristics of Li6.75La3Zr1.75Ta0.25O12 Thin Films Deposited by Nanosecond PLD

“…For PLD experiments, the ambient pressure has strong impact on the condensation rate from the plasma, film growth rate, and film quality, because it affects the plasma plume expansion, composition and transport of the ablated species to the substrate. PLD depositions carried out under high pressures leads to compact and dense films whereas lower pressures can promote the film adhesion over the substrate or reduce impurity incorporation [3]. Furthermore, the background gas plays an important role in the film growth and properties, since it helps to create a controlled environment, shielding the ablated material from reactive species or contaminants during the deposition, like the inevitable water moisture or hydrocarbons, leading to high purity films with improved properties.…”

“…PLD allows deposition within a broad pressure range, spanning from ultra-high vacuum to ambient pressure [2]. Moreover, this technique enables the deposition of the widest range of accessible material compositions and stands as the most efficient method for materials with complex chemical compositions [2,3]. However, it requires careful optimization of the experimental parameters to achieve high-quality crystalline films with the desired composition.…”

“…This process depletes the plasma from lighter elements in the target-to-substrate direction with respect to the heavier ones. Therefore, despite their larger velocity, the relative concentration of lither elements in the deposited film is smaller compared to the heavier ones due to scattering [2][3][4]. This phenomenon unavoidably contributes to considerable compositional deviation: this is true for solid state lithium ionic conductors like Li 7 La 3 Zr 2 O 12 (LLZO) where very light atoms, e.g., Li, and very heavy ones, e.g., Zr and La, coexist.…”

Ultrashort and short-pulse laser ablation for chemical element analysis and thin film deposition of complex materials

“…Thin films are grown by deposition of atomic and molecular species ablated from the target and/or species formed in the plasma plume and of droplets formed by vapor phase condensation. This pulsed-laser deposition (PLD) technique is employed for thin film synthesis of different classes of multi-element materials such as oxidic perovskites [1][2][3][4], transition metal dichalcogenides [5] and many others. The quality of PLD thin films with respect to material phase formation, stoichiometry, crystallinity, lattice orientation, defect density, surface morphology, and functional properties (e.g., piezoelectric, electric, magnetic, ferroic, tribological, bio-compatible, anti-bacterial, etc.)…”