Laser-induced electronic processes on GaP (110) surfaces: Particle emission and ablation initiated by defects.
Laser-induced electronic processes on GaP (110) surfaces: Particle emission and ablation initiated by defects.
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GaP (110) 表面上的激光诱导电子过程：由缺陷引发的粒子发射和烧蚀。
DOI：
10.1103/physrevb.45.8424
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Itoh
中科院分区：
文献类型：
--
作者：
Hattori;Okano;Nakai;Itoh
我们利用激光脉冲对GaP（110）表面发射的光子能量进行了高敏感度测量，测量光子能量高于间接带隙能量${\mathit{E}}_{\mathit{G}}$（范围I），低于${\mathit{E}}_{\mathit{V}\mathit{S} $（范围II），低于${\mathit{E}}_{\mathit{V}\mathit{S} $（范围III），低于${\mathit{V}}$。在烧蚀阈值以下，我们发现能量范围II和III的激光脉冲诱导粒子发射，随着激光在同一点上的重复发射，粒子的产率降低。产率随枝数的变化呈快速(A)和缓慢(S)递减。通过${\mathrm{Ar}}^{+}$轰击增强了A分量，并通过后续退火降低了A分量。对脉冲宽度依赖性的测量表明，产率是由A组分的影响度来缩放的。A和S组分的产率都是通量的超线性函数，表现出明显的阈值激光通量。发现A组分的阈值激光能量密度小于S组分。屈服-影响关系也可以拟合为幂函数：A分量的幂指数为2\char21{}3， S分量的幂指数为4\char21{}6。这些成分不是由能量范围i的光子诱导的。在烧蚀阈值以上，发现通过重复激光脉冲在同一点上的产率增加。在能量范围I和II中，光子的烧蚀阈值几乎相同，而在能量范围III中，光子的烧蚀阈值是分散的。结果被解释为通过多电子-空穴局域化使表面缺陷附近的松散束缚原子的键断裂。缺陷分为三种类型：粘原子型、台阶上的扭结型和空位型。A和S组分分别由合原子型和扭结型缺陷引起，激光烧蚀由空位引起。提出了一种局部化模型。
We have carried out high-sensitivity measurements of ${\mathrm{Ga}}^{0}$ emission from the GaP (110) surface by laser pulses of photon energies above the indirect-band-gap energy ${\mathit{E}}_{\mathit{G}}$ (range I), below ${\mathit{E}}_{\mathit{G}}$ but above the energy gap ${\mathit{E}}_{\mathit{V}\mathit{S}}$ between the valence band and the unoccupied surface band (range II), and below ${\mathit{E}}_{\mathit{V}\mathit{S}}$ (range III). Below the ablation threshold, we find that laser pulses of energy ranges II and III induce particle emission, the yield of which is reduced as the laser shots are repeated on the same spot. The dependence of the yield on the number of shots shows rapidly (A) and slowly (S) decreasing components. The A component is found to be enhanced by ${\mathrm{Ar}}^{+}$ bombardment and reduced by subsequent annealing. Measurements of the dependence of the pulse width show that the yield is scaled by the fluence for the A component. The yields for both A and S components are superlinear functions of fluence, exhibiting apparent threshold laser fluences. The threshold laser fluence for the A component is found to be smaller than that for the S component. The yield-fluence relations can also be fitted to power functions: The power index for the A component is 2\char21{}3 and, for the S component, 4\char21{}6. These components are not induced by photons in energy range I. Above the ablation threshold the yield on the same spot is found to increase by repeating laser pulses. Nearly the same ablation threshold fluence was observed for photons in energy ranges I and II, while the ablation threshold is scattered for photons in energy range III. The results are interpreted in terms of a breaking of the bonds of loosely bound atoms near defects on surfaces by multiple electron-hole localization. Three types of defects are differentiated: adatom type, kink type on steps, and vacancy type. The A and S components are ascribed to be initiated by the adatom- and kink-type defects, respectively, and the laser ablation is ascribed to be initiated by vacancies. A model of localization is suggested.