Nanocrystals depth pro®ling by means of Cs  in negative polarity with dual beam ToF-SIMS M. Perego * , S. Ferrari, S. Spiga, M. Fanciulli Laboratorio MDM-INFM, Via Olivetti 2, 20041 Agrate Brianza, MI, Italy Abstract Wedevelopedanempiricalmethodtoperformquantitativedepthpro®lesofantimonynanocrystalsembeddedinsiliconoxide with a dual beam ToF-SIMS using Cs  in negativepolarity. We assumed that the Cs concentration in the oxide layer is constant andthevariationinsignalintensitiesaredueessentiallytomatrixeffectsrelatedtochangesintheoxidationstateofantimony.A parameter that describes the oxidation state of the species of interest was established on the basis of the relative intensity of different antimony containing clusters. We developed a quantitative relationship between this parameter and the ionization probability.InthiswayitwaspossibletocorrecttheSbsignalobtainingamatrixindependentsignalthatgiveusthepossibilityto realize a quantitative depth pro®le. # 2002 Elsevier Science B.V. All rights reserved. Keywords: ToF-SIMS; Antimony nanocrystals 1. Introduction Nanocrystals embedded in dielectric materials attract great interest in microelectronics due to their novel electrical and optical properties. Ion beam synthesis of nanocrystals in SiO 2 represents a very powerful and versatile technique compatible with present silicon technology. Structural characterization of these systems is a challenging task because of the high depth resolution and high sensivity required. TheuseofdualbeamToF-SIMSdepthpro®ling,with the ability to decouple sputtering from the analysis gun, can improve depth resolution and very good sensitivity can be achieved using Cs  in negative polar- ity. The drawback of this kind of con®guration is the dif®culty in controlling intensity variations in the pro- ®le, caused by matrix effects; in particular cesium concentration in the matrix as well as oxidation state of the species of interest are affecting the signals. In this work we address these two issues and we develop a method to control matrix effects and to obtain quantitative depth pro®les in the heterogenous systems. We apply this method to thin silicon oxide layers after high dose Sb implantation and Sb nano- crystal formation by thermal annealing. 2. Experimental The samples considered in this paper are SiO 2 thin ®lms grown on (1 0 0) silicon substrate and implanted with 121 Sb at 10 keV and dose 5  10 15 atoms/cm 2 . Different oxides have been considered. After implan- tation samples have been annealed in RTP (rapid thermal process) or in furnace to induce the formation of nanocrystals. All the details about thermal treat- ments are reported in Table 1. Applied Surface Science 203±204 (2003) 110±113 * Corresponding author. E-mail address: mperego@mdmlab.mi.infm.it (M. Perego). 0169-4332/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0169-4332(02)00710-9