TUBITAK-BILGEM, National Research Institute of Electronics, Gebze, Turkey.
Nanotechnology. 2011 Jun 10;22(23):235307. doi: 10.1088/0957-4484/22/23/235307. Epub 2011 Apr 12.
The physical properties of black silicon (b-Si) formed on Si wafers by reactive ion etching in chlorine plasma are reported in an attempt to clarify the formation mechanism and the origin of the observed optical and electrical phenomena, which are promising for a variety of applications. The b-Si consisting of high density and high aspect ratio sub-micron length whiskers or pillars with tip diameters of well under 3 nm exhibits strong photoluminescence (PL) both in the visible and the infrared, which is interpreted in conjunction with defects, confinement effects and near band-edge emission. Structural analysis indicates that the whiskers are all crystalline and encapsulated by a thin Si oxide layer. The infrared vibrational spectrum of Si-O-Si bondings in terms of transverse-optic (TO) and longitudinal-optic (LO) phonons indicates that disorder induced LO-TO optical mode coupling can be an effective tool in assessing the structural quality of the b-Si. The same phonons are likely coupled to electrons in visible region PL transitions. Field emission properties of these nanoscopic features are demonstrated indicating the influence of the tip shape on the emission. Overall properties are discussed in terms of the surface morphology of the nanowhiskers.
本文报道了在氯等离子体反应离子刻蚀中，在硅片上形成的黑硅（b-Si）的物理性质，试图阐明其形成机制和观察到的光学和电学现象的起源，这些性质在各种应用中很有前景。由高密度、高纵横比的亚微米长度的晶须或柱体组成的 b-Si，其尖端直径远小于 3nm，具有很强的可见光和红外光致发光（PL），这与缺陷、限制效应和近带边发射有关。结构分析表明，晶须都是结晶的，并被一层薄的氧化硅层包裹着。硅氧硅键的红外振动光谱，根据横向光学（TO）和纵向光学（LO）声子，表明无序诱导的 LO-TO 光学模式耦合可以成为评估 b-Si 结构质量的有效工具。相同的声子可能与可见光区域 PL 跃迁中的电子耦合。这些纳米结构的场发射特性得到了证明，表明了尖端形状对发射的影响。整体性质是根据纳米晶须的表面形貌来讨论的。
