Temporally and spatially resolved plasma spectroscopy in pulsed laser deposition of ultra-thin boron nitride films

Abstract

Physical vapor deposition (PVD) has recently been investigated as a viable, alternative growth technique for two-dimensional materials with multiple benefits over other vapor deposition synthesis methods. The high kinetic energies and chemical reactivities of the condensing species formed from PVD processes can facilitate growth over large areas and at reduced substrate temperatures. In this study, chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated from a boron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated. Time resolved spectroscopy and wavelength specific imaging were used to identify and track atomic neutral and ionized species including B þ , B*, N þ , N*, and molecular species including N 2 *, N 2 þ , and BN. Formation and decay of these species formed both from ablation of the target and from interactions with the background gas were investigated and provided insights into fundamental growth mechanisms of continuous, amorphous boron nitride thin films. The correlation of the plasma diagnostic results with film chemical composition and thickness uniformity studies helped to identify that a predominant mechanism for BN film formation is condensation surface recombination of boron ions and neutral atomic nitrogen species. These species arrive nearly simultaneously to the substrate location, and BN formation occurs microseconds before arrival of majority of N þ ions generated by plume collisions with background molecular nitrogen. The energetic nature and extended dwelling time of incident N þ ions at the substrate location was found to negatively impact resulting BN film stoichiometry and thickness. Growth of stoichiometric films was optimized at enriched concentrations of ionized boron and neutral atomic nitrogen in plasma near the condensation surface, providing few nanometer thick films with 1:1 BN stoichiometry and good thicknesses uniformity over macroscopic areas. V C 2015 AIP Publishing LLC. [http://dx.

Amorphous Boron Nitride: A Universal, Ultrathin Dielectric For 2D Nanoelectronics

“…[ 38,39 ] Briefl y, a 248 nm KrF pulsed UV laser enters a nitrogen fi lled vacuum chamber through a focusing lens and strikes a rotating boron nitride target, as seen in a schematic [ 32 ] 2.27 [ 8 ] -Dielectric constant ≈3.5 [ 14 ] 3 ± 1.0 [ 33 ] 6.85 [ 32 ] 3.9 [ 8 ] 5.9 ± 0.7 A comprehensive description of the process development can be found in prior work.…”

“…The nonequilibrium, localized heating of the target surface with the laser beam rapidly vaporizes boron and nitrogen species and in so doing, a high energy plasma is formed. [ 38,39 ] Benefi ts of this optimized PLD approach include the inherent ability to commercialize PLD processes to large areas, [ 40,41 ] (Figure 1 b shows a -BN grown on a Si/SiO 2 wafer with a cross-section from a similar wafer), stoichiometric a -BN growth at signifi cantly reduced temperatures from room temperature to 200 °C on a diverse range of substrates (Figure 1 c), and all without modifying the required deposition conditions. The concentrations and time dependent peak occurrences are controlled by laser power density, background gas pressure and the separation, or "working", distance from target to substrate.…”

Magnetic field argon ion filtering for pulsed magnetron sputtering growth of two-dimensional MoS2

“…Spectroscopic studies of plasma chemistry and element specific plasma imaging were performed under arrangements similar to those described previously for laser ablated plasma studies in ultra-thin BN growth [42]. A quartz window (transmittance cut-off about 180 nm) was arranged with a view parallel to the substrate surface and perpendicular to the substrate-magnetron axis, capturing light emitted from the plasma region between magnetron target and the substrate location.…”

Ångström-Scale, Atomically Thin 2D Materials for Corrosion Mitigation and Passivation

“…Conversely, contrary to theoretical predictions, Stone-Wales defects have not been found experimentally in hBN [114][115][116][117]. Various 2D material preparation techniques have been developed, which can be classified generally into two categories: top-down techniques (i.e., exfoliation via mechanical [19,[93][94][95], liquid [96,97] or chemical [98,99] means, electro-ablation [100]), and bottom-up techniques (i.e., atomic layer deposition (ALD) [101,102], pulsed laser deposition (PLD) [103,104], chemical vapor deposition (CVD) [105,106]). Typically, exfoliation generates 2D material flakes with small lateral sizes and poor dimensional control.…”