Intrinsic Maximum Light Absorption in Laser-Field-Driven Growth of Highly Ordered Silicon Nanowire Arrays

Abstract

We provide direct experimental evidence for a state-selection principle in a far-from-equilibrium system. Using the laser-driven growth of silicon nanowires as a uniquely clean and quantifiable platform, we show that a long-range ordered array emerges as the system spontaneously selects the periodicity that maximizes its collective light absorption. This establishes a direct, measurable link between a maximum dissipation/absorption principle and emergent structural order. Our results thus offer a concrete test for models of non-equilibrium self-organization.

Figures (4)

• Figure 1: Laser driven growth of Silicon nanowire array. (a) Schematic illustration of the spontaneous growth of Si nanowires driven by laser irradiation. (b) Typical SEM image of a SiNWA grown on an Al2O3 substrate, induced by a long silver wire. The red arrow indicates the polarization direction of incident laser. (c-e) Cross sectional TEM images of a SiNWA with a period of 274nm grown on Al2O3 substrate at a laser peak intensity of 5.4e9Wcm, with a SiH4 flow rate of 30 sccm and an H2 flow rate of 100 sccm. (f, g) SiNWA with a period of 279 nm, grown under the same conditions but with a reduced silane flow rate of 6 sccm.
• Figure 2: Silicon nanowires maximize light absorption by selecting a specific array periodicity. (a) Calculated absorption per nanowire versus array period, using the experimentally measured nanowire cross-section as the repeating unit. The absorption peak aligns precisely with the experimentally observed period (vertical dashed line). (b),(c) Cross-sectional electric field intensity distribution, $(E/E_0)^2$, simulated for the nanowire array (nanowire unit cell: r=50.8 nm, h=39 nm). The field is strongly enhanced inside the nanowire at (b) the optimal period (274 nm), corresponding to the absorption peak, but is significantly weaker at (c) a non-optimal period (200 nm).
• Figure 3: Silicon nanowires growth driven by tip-field enhancement and multiphoton absorption. (a) SEM image of the initial growth stage, where a Ag nanoparticle is encapsulated by silicon. (b) A silicon nanowire emerges from the Ag particle and propagates along the Al2O3 substrate. (c) A fully grown Silicon nanowire exhibiting a uniform diameter and a sharp, well-defined tip. (d) The dependence of the nanowire growth rate on the peak intensity of the incident laser.(e) Simulated electric field intensity distribution at the SiNW tip, 2nm above the substrate, for an incident laser polarized parallel to the nanowire length. (f) Demonstration of controlled, byproduct-free growth of isolated silicon nanowires.
• Figure 4: Spontaneous optimal array formation guided by maximum energy absorption. (a) Two and three silicon nanowires arrays were grown from silver wires with lengths of 300 nm (left) and 580 nm (right), respectively. (b-d) Simulated cross-sectional electric field distributions for one, two, and three silicon nanowires, respectively, under laser irradiation. Dashed lines indicate nanowires positions. (e, f) SEM images of the initial Si growth stages on Ag wires, showing the transition from small Si “beards” to periodic, short nanowires. (g-i) SEM images of SiNW arrays grown from Ag particle arrays with periodicities of (g) 140 nm, (h) 240 nm, and (i) 280 nm.