Milan Mikula

On the topographic and optical properties of SiC/SiO2 surfaces

The roughness of the semiconductor surface substantially influences properties of the whole structure, especially when thin films are created. In our work 3C SiC, 4H SiC and Si/a-SiC:H/SiO2 structures treated by various oxidation a passivation procedures are studied by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). Surface roughness properties are studied by fractal geometry methods. The complexity of the analysed surface is sensitive to the oxidation and passivation steps and the proposed fractal complexity measure values enable quantification of the fine surface changes. We also determined the optical properties of oxidized and passivated samples by using visual modelling and stochastic optimization.

Effect of HCN passivation on silicon oxide thin layer

Silicon dioxide layers are materials with unique dielectric and interface properties. We investigated samples with SiO2 layers prepared with nitric acid oxidation of silicon (NAOS) method and with natural oxide layer after passivation with HCN aqueous solution. Samples were investigated with atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. We found higher roughness of layers after passivation and different effects of HCN passivation on samples. From the measurements, we conclude that HCN passivation influences structural and optical properties of SiO2 layer.

Regarding the Optical Properties of Porous Layers Prepared on Si Substrates

The paper deals with the complex refractive index and photoluminescence in the IR-VIS light region of two sample types (i) black p-type silicon (BSi) produced by the surface structure chemical transfer method using Pt catalytic mesh, and (ii) porous p-type silicon prepared by standard electrochemical etching. We present, compare, and discuss the values of the IR-VIS complex refractive index obtained by calculation using the Kramers-Kronig transformation and the photoluminescence properties thereof. The results indicate that differences between the optical properties of the BSi and the porous Si are given by (a) the oxidation procedure of BSi, (b) the thickness of the formed black and porous Si layer, and by (c) the porosity of both layer types. We assume that the photoluminescence signal generated by oxidized BSi structures can be mainly related to the quantum confinement effect, while the photoluminescence of the porous p-type Si is caused by the optical activity of the SiOxHy compounds covering its surface region.

About complex refractive index of black Si

Abstract The paper deals with the complex refractive index in the IR light region of two types of samples (i) as prepared black silicon, and (ii) thermally oxidized black silicon (BSi) nano-crystalline specimens produced both by the surface structure chemical transfer method using catalytic Ag evaporated spots (as prepared sample) and by the catalytic Pt catalytic mesh (thermally oxidized sample). We present, compare, and discuss the values of the IR complex refractive index obtained by calculation using the Kramers-Krönig transformation. Results indicate that small differences between optical properties of as prepared black Si and thermally oxidized BSi are given by: (i) – oxidation procedure, (ii) – thickness of the formed black Si layer, mainly, not by utilization of different catalytic metals, and by iii) the different thickness. Contamination of the surface by different catalytic metals contributes almost equally to the calculated values of the corresponding complex refractive index.

Morphology and FT IR spectra of porous silicon

Abstract The morphology and chemical bods of p-type and n-type porous Si was compared. The surface of n-type sample is smooth, homogenous without any features. The surface of p-type sample reveals micrometer-sized islands. FTIR investigation reveals various distribution of SiOxHy complexes in both p-and n-type samples. From the conditions leading to porous silicon layer formation (the presence of holes) we suggest both SiOxHy and SiFxHy complexes in the layer.

Physical Properties and Light-Related Applications of Black Silicon Structures

This contribution deals with the black silicon (BS) nanocrystalline specimens produced using the surface structure chemical transfer method (SSCT). This method can produce a nanocrystalline Si black color layer on c-Si with a thickness range of ~50 nm to ~300 nm via the contact of c-Si immersed in the chemical solution HF + H2O2 with a catalytic mesh. The photoluminescence properties are related to the formation of nanocrystals, the structural properties of which are similar to those formed on the back of a sawn Si wafer and the resulting splitting of large Si crystals. X-ray diffraction of the Si front and back sides confirms the dominant reflection of the 311 Si crystalline planes. We suppose that the formation of the black silicon over-layer is pre-determined by the crystalline defects induced by the applied sawing procedure, even though saw damage (defects introduced by the applied sawing procedure) is not necessary for the SSCT method. The formation of the pn type Si solar cell is presented, including black silicon over-layer and without antireflection coating, with efficiency of ~19.1%.

Interaction of KCN solutions with Si-based thin films

This contribution deals with the interaction of cyanide solutions with two types of double-layer structures. A 0.1 M KCN methanol solution, one of the very strong alkaline solutions, was used for t...