ISSN 1027-4510, Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2012, Vol. 6, No. 5, pp. 776–781. © Pleiades Publishing, Ltd., 2012. Original Russian Text © V.M. Kashkarov, A.S. Len’shin, P.V. Seredin, B.L. Agapov, V.N. Tsipenuk, 2012, published in Poverkhnost’. Rentgenovskie, Sinkhrotronnye i Neitronnye Issledovaniya, 2012, No. 9, pp. 80–86. 776 INTRODUCTION Porous silicon (PS) is a material with unique phys- ical-chemical properties, which has a large number of pores and is characterized by a well-developed surface with a specific area reaching 400–600 m 2 per 1 cm 3 [1]. The transverse pore size varies from several nanometers to several micrometers, and the porous layer thickness, which depends on the treatment dura- tion, can be tens of micrometers. A porous layer formed on the surface of a Si single-crystal commonly contains nanosized clusters and silicon quantum wires, the surfaces of which are partially oxidized and covered by hydrogen atoms and hydroxyl groups. In contrast to single-crystalline silicon, the presence of these components in a porous layer initiates the rather intense photoluminescence of the given material in the visible spectral region [2]. The high specific surface of porous silicon provides a high sorption capacity. This property is very attractive from the standpoint of the creation of various PS-based sensors [3, 4]. A porous layer on single-crystalline silicon can be obtained rather easily by electrochemical etching in alcohol solutions based on hydrofluoric acid. In this process, the size and depth of pores and the layer porosity (the ratio between the pore volume and the total layer volume) can be controlled. Moreover, the composition of the pore surface can be controlled to some extent by changing the electrolyte composition. However, weak silicon–hydrogen bonds on the pore surface lead to the temporal instability of the PS’s properties [5, 6]. The gradual oxidation of a porous layer due to Si–H bond breakage, followed by their replacement with silicon–oxygen bonds and hydroxyl groups, leads to a decrease in photoluminescence, deteriorates the sorption characteristics of the mate- rial, and makes it impossible to create high-quality PS-based sensors. Hence, in recent years, researchers have actively sought for methods of PS surface passivation that would enable the prevention of surface layer deteriora- tion in pores. On the one hand, Ps surface modifica- tion enables us to obtain certain parameters, which are important in the development of sensing devices and substrates and can be employed to determine micron- and submicron-scale biological objects, i.e., bacteria, viruses, and even DNA fragments [7]. To prevent sur- face deterioration during PS storage in air, different variants of surface passivation have been proposed. They involve the rapid oxidation of samples in an oxy- gen environment, surface coating with thin polymeric films, and so on [8, 9]. However, all the aforementioned methods necessi- tate complicated technological operations with allow- ance for the relatively low mechanical strength and chemical stability of PS to heating and coating of the pore surfaces. The authors of [10, 11] have suggested that PS surfaces be treated in different organic com- pounds. Then, in their opinion, layers enriched with Si–C bonds, which are stable in time and do not diminish the photoluminescent properties of a mate- rial, will be formed directly on the pore surfaces [10]. In [12], it was demonstrated that PS nanocrystals treated in polyacrylic acid have stable photolumines- cence for a long time. In this work, the electronic structure and morphol- ogy of PS and corrugated silicon are investigated. The PS samples were prepared by electrochemical etching under different conditions. Corrugated silicon sam- ples were produced by chemical etching before and after treatment in a polyacrylic acid solution. Chemical Modification of Porous and Corrugated Silicon Surfaces in Polyacrylic Acid Solutions V. M. Kashkarov, A. S. Len’shin, P. V. Seredin, B. L. Agapov, and V. N. Tsipenuk Voronezh State University, Voronezh, Russia Received June 20, 2011 Abstract—The chemical modification of porous silicon (PS) surfaces makes it possible to eliminate weak sil- icon–hydrogen bonds and prevent the formation of Si–O and Si–OH groups deep in pores and on a corru- gated silicon surface. Hence, the effect of PS aging is not observed during its storage in air, and the porous layer’s composition is stable. Surfaces have been modified in polyacrylic acid solutions. The surface compo- sition is analyzed on the basis of X-ray absorption spectra, and the morphology is investigated via scanning electron microscopy. It has been ascertained that the composition and morphology of a surface treated in polyacrylic acid solutions depend on the PS preparation method. DOI: 10.1134/S1027451012090078