Figure 1

(a) Contrast at a step (arrowed) at the catalyst/nanowire interface, observed in a bright-field TEM video. The video was recorded at 30 frames per second during growth of a ${\mathrm{Cu}}_3\mathrm{Si}$-catalyzed 61 nm diameter Si nanowire at $530°\mathrm{C}$ and a partial pressure of $2.4\times {10}^{-7}\mathrm{Torr}$ disilane. The field of view includes only part of the interface. (b) An instance in which two steps are present in the field of view at $1.5\times {10}^{-6}\mathrm{Torr}$ disilane. (c) The nanowire growth model. The dotted arrow indicates the measured location of the step, $x$, and the dashed arrow indicates the electron beam direction, in the plane of the interface and perpendicular to $x$. (d) The location of steps measured at $530°\mathrm{C}$ and $1.0\times {10}^{-6}\mathrm{Torr}$ disilane. Two fields of view are superimposed (blue and green) to illustrate complete step flow curves. The incubation time is indicated by the arrow. The solid and dashed curves are results of Eqs. (4, 5, 6, 7) with $\varphi =0.2$, $k=\infty$ and $\varphi =0.3$, $k=0.14$, respectively. The dotted line shows the excess concentration of Si for $\varphi =0.3$, $k=0.14$. (e) Measurement of interface position during VLS growth of a 44 nm diameter AuSi-catalyzed Si nanowire at $550°\mathrm{C}$ and $4\times {10}^{-7}\mathrm{Torr}$ disilane. Formation of a new layer is apparent as a rapid advance of the catalyst/Si interface by 0.3 nm. The incubation time between such events is $\sim 12\mathrm{s}$.Reuse & Permissions

Figure 2

Simulations of step flow (solid lines) with different $\varphi$ values and $k=\infty$. The excess concentration of Si, $c-c_0$, is plotted as dotted lines. Arrows indicate the incubation period.Reuse & Permissions