Pulsed laser deposition to synthesize the bridge structure of artificial nacre: Comparison of nano- and femtosecond lasers

Abstract

Nature offers inspiration to new adaptive technologies that allow us to build amazing shapes and structures such as nacre using synthetic materials. Consequently, we have designed a pulsed laser ablation manufacturing process involving thin film deposition and micro-machining to create hard/soft layered “brick-bridge-mortar” nacre of AlMgB14 (hard phase) with Ti (soft phase). In this paper, we report pulsed laser deposition (PLD) to mimic brick and bridge structures of natural nacre in AlMgB14. Particulate formation inherent in PLD is exploited to develop the bridge structure. Mechanical behavior analysis of the AlMgB14/Ti system revealed that the brick is to be 250 nm thick, 9 μm lateral dimensions while the bridge (particle) is to have a diameter of 500 nm for a performance equivalent to natural nacre. Both nanosecond (ns) and femtosecond (fs) pulsed lasers were employed for PLD in an iterative approach that involves varying pulse energy, pulse repetition rate, and target-to-substrate distance to achieve the desired brick and bridge characteristics. Scanning electron microscopy, x-ray photoelectron spectroscopy, and optical profilometer were used to evaluate the film thickness, particle size and density, stoichiometry, and surface roughness of thin films. Results indicated that both ns-pulsed and fs-pulsed lasers produce the desired nacre features. However, each laser may be chosen for different reasons: fs-pulsed laser is preferred for much shorter deposition time, better stoichiometry, uniform-sized particles, and uniform film thickness, while ns-pulsed laser is favored for industrial acceptance, reliability, ease of handling, and low cost.

Picosecond Laser Micromachining of Ultra-Hard AlMgB₁₄ Thin Films

“…The laser and scanner were synchronously controlled. Superhard thin films of AlMgB 14 were prepared on 25 mm diameter silicon wafer by the standard excimer (248 nm) pulsed laser deposition technique described elsewhere [13]. The film thickness was about 100 nm with few particulates and a surface roughness of 1 nm in Ra scale.…”

Fabricating functionally graded films with designed gradient profiles using pulsed laser deposition

“…Among many deposition techniques, pulsed laser deposition (PLD) is regarded as one of the most capable physical vapor deposition methods because materials with complex stoichiometry can be ablated and deposited by using a high intensity laser. [1][2][3][4][5] One important research topic in pulsed laser deposition is the fabrication and use of functionally graded films. This is a popular technique to fabricate a film with advanced and/or improved functionality by designing a film with more than one material.…”