J. Servat

Nanometer-scale oxidation of Si(100) surfaces by tapping mode atomic force microscopy

The nanometer‐scale oxidation of Si(100) surfaces in air is performed with an atomic force microscope working in tapping mode. Applying a positive voltage to the sample with respect to the tip, two kinds of modifications are induced on the sample: grown silicon oxide mounds less than 5 nm high and mounds higher than 10 nm (which are assumed to be gold depositions). The threshold voltage necessary to produce the modification is studied as a function of the average tip‐to‐sample distance.

Nature of multilayer steps on the {100} cleavage planes of MgO single crystals

Abstract The results of an AFM study of the nature of multilayer steps on the {100} cleavage faces of MgO crystals is described and discussed. The results show that (i) multilayer cleavage steps of a width between 55 and 590 nm and of a slope between about 1 and 8° are stable, (ii) the terminal planes of multilayer steps are composed of high-index vicinal faces with indices (7 0 1), (42 0 1) and (77 0 1) for the 〈010〉 steps with respect to the (100) cleavage, which do not correspond to the low-index planes of the equilibrium form of MgO crystals, and (iii) that the curved parts of the profile of a multilayer cleavage step in its upper and lower regions extend to a distance equal to the width of the step.

First stages of platinum electroless deposition on silicon (100) from hydrogen fluoride solutions studied by AFM

The first stages of platinum electroless deposition on p-Si (100) from hydrogen fluoride (HF) solutions are studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), electron dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Platinum nuclei are deposited on a silicon substrate by simple immersion in an aqueous HF solution containing a platinum salt. Tapping-mode AFM and TEM have been used to characterize the samples morphologically, and EDS and XPS to identify the chemical nature of the main features. Platinum silicide formation has been detected for the first time in this kind of process, suggesting a competition between the deposition of pure metal and the formation of its silicide.

Nanometer scale lithography of silicon(100) surfaces using tapping mode atomic force microscopy

Si(100) surfaces have been successfully oxidized at nanometer scale using an atomic force microscope working in tapping mode (TMAFM). To modify the surface, gold coated tips and chromium–gold coated tips have been used in order to apply a positive voltage to the sample against the grounded tip. A silicon oxide line of ∼10 nm lateral dimensions can be routinely grown on Si(100) surfaces by TMAFM, at a tip velocity as high as 0.1 mm/s. Pattern dimensions have been measured for different tip velocities and applied voltages and a tip velocity of up to 10 mm/s has been predicted. The patterns have been successfully used as a lithographic mask for a wet chemical etching.

Atomic force microscopy observation of the first stages of diamond growth on silicon

Abstract The first stages of diamond growth on scratched silicon substrates were studied by atomic force microscopy (AFM). Samples were obtained by both hot filament and microwave plasma CVD methods at short deposition times prior to coalescence. It was observed that, after an incubation time, diamond nanocrystals nucleated onto the scratches produced by diamond paste polishing. The Raman spectra of the crystals showed different bands associated with several carbon phases. Simultaneous with diamond growth, we detected an etching effect of the silicon surface attributed to the atomic hydrogen present in the activated gas.

Electrodeposition of Zinc‐Cobalt Alloys Tapping Mode AFM Technique Applied to Study the Initial Stages of Deposition

The first stages of electrodeposition of zinc-cobalt alloys on highly oriented pyro-graphite are studied by tapping mode atomic force microscopy (AFM), scanning electron microscopy, and electrochemical analysis. Low Zn(II)/Co(II) ratio (1/9) solutions are selected for this study. Potentiostatic deposition begins through the formation of randomly distributed zinc-rich nuclei on the surface, showing exclusion areas around the larger nuclei and preferential nucleation at the kink sites. At long deposition times an incipient dendritic growth, related to the initiation of pure cobalt deposition is observed. A simple AFM tip deconvolution model is used to obtain the actual dimensions of both the tip itself and the deposited nuclei. The nuclei growth mechanism observes lateral diffusion and aggregation and the formation of emerging nuclei on top of yet consolidated nuclei.

Atomic force microscopy study of nanoindentation deformation and indentation size effect in MgO crystals

The dependences of various nanoindentation parameters, such as depth of penetration d, indentation diameter a, deformation zone radius R, and height h of hills piled up around indents, on applied load were investigated for the initial (unrecovered) stage of indentation of the (100) cleavage faces of MgO crystals by square pyramidal Si tips for loads up to 10 mN using atomic force microscopy. The experimental data are analyzed using theories of elastic and plastic deformation. The results revealed that (i) a, R, and h linearly increase with d; (ii) the development of indentation size and deformation zone and the formation of hills are two different processes; (iii) the load dependence of nanohardness shows the normal indentation size effect (i.e., the hardness increases with a decrease in load); and (iv) there is an absence of plastic deformation involving the formation of slip lines around the indentations. It is found that Johnson’s cavity model of elastic–plastic boundary satisfactorily explains the experimental data. The formation of hills around indentations is also consistent with a new model (i.e., indentation crater model) based on the concept of piling up of material of indentation cavity as hills.

Enhanced surface atomic step motion observed in real time after nanoindentation of NaCl(100)

Abstract The nanometer-scale indentation of a crystalline surface produces nanostructures that evolve on a timescale that is inaccessible to existing imaging methods for the vast majority of surfaces. We have been able to observe the dynamic evolution of the freshly cleaved surface of a NaCl(100) crystal after indentation with an atomic force microscope (AFM) in air. Here we present sequential AFM images featuring vertical atomic resolution which show that atomic terrace motion is greatly enhanced by the AFM indentation. Moreover, some of the nanometric features generated by the indentation become reassimilated into the crystalline surface structure of the surroundings of the indentation over a period of time of the order of several minutes.

AFM study of etching of cleaved {1 0 0} faces of L-arginine phosphate monohydrate single crystals I. Dislocation etch pits and step bunching

Abstract The formation of dislocation etch pits and the process of coalescence of dissolution steps composing the walls of dislocation etch pits on the etched {1 0 0} cleavage faces of L-arginine phosphate (LAP) single crystals was studied by using atomic force microscopy (AFM). The results show that (1) etch pits at edge and screw dislocations are formed by repeated two-dimensional nucleation mechanism, (2) the values of different slopes of etch pits in regions close to dislocation lines are due to differences in the stress fields of dislocations producing the etch pits, and that (3) the process of step bunching is statistical in nature.

AFM study of etching of cleaved {1 0 0} faces of L-arginine phosphate monohydrate single crystals II. Two-dimensional nucleation, formation of spiral elevations and decoration of dissolution layers

Observations on the formation of two-dimensional (2D) etch pits, the decoration of dissolution steps and the formation of dissolution spiral elevations on the etched {1 0 0} cleavage faces of L-arginine phosphate (LAP) single crystals made by using atomic force microscopy (AFM) are described and discussed. It was found that spiral elevations at the points of emergence of screw dislocations are formed during dissolution by the retreating of their elementary steps around decorated centres, and that there are gradients in undersaturation on the surface in the vicinity of spiral elevation centres, the maximum undersaturation being at spiral centres.