Monitoring thin film growth

Atomic force microscopy (AFM) is a high-resolution 3D imaging technique capable of measuring topographical features to less than 1 nm (Binning et al., 1986). A cantilever with a sharp tip is brought into contact with the surface, in which the force between the tip and the surface results in deflection of the cantilever. The cantilever is rastered over 

Thin Film Coatings for Biomaterials and Biomedical Applications 

AFM can be used to follow the deposition of thin films over time. Simple thickness measurements can be performed by either scoring the film with a scalpel after deposition or masking part of the substrate before deposition of the film, and measuring the height of the step created. In Fig. 2.5, plasma polymer films grown from acrylic acid monomer are shown to grow initially as discrete islands, which then coalesce and eventually form a flat, pinhole-free film after approximately 240 s. This result is contrary to the often-stated view of plasma deposition that films always grow as a conformal layer. 

Other measurements to assess film quahty are also possible using AFM. The mechanical properties of films can be quantified by applying a force to the surface through the tip and measuring the depth of the indent created on the surface. Experimental data of indentation depth (5) versus force (F) can be applied to the Hertz equation (Eq. [2.4]) using the fitting parameter a, which is related to Young s modulus ( ), as shown in Eq. [2.5] (Choukourov et al., 2012). 

With developments in instrumentation, AFM has become a relatively inexpensive and simple tool for assessing thin films. Its major disadvantage is that it cannot be performed in situ, so measurement is performed after processing. 

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Excitonic absorption and photoluminescence (PL) of nanoparticles of zincblende structured 1-Vll semiconductors (CuX and Agl, X = Cl, Br, I) are briefly reviewed. In Cu-stabilized Agl thin films formed by ambient iodination, exciton absorption sensibly monitors the film growth, where Cu favors enhanced PL involving excitons in quasi-free Agl nanoparticles. In Sb-doped Agl thin films, Sb achieves interface stabilized, more retarded Agl particle growth while causing PL due to donor-acceptor recombination. 

C. Argile and G.E. Rhead. Adsorbed Layer and Thin Film Growth Modes Monitored by Auger Electron Spectroscopy. Surf. Sci. Rep. 10 277 (1989). 

In comparing the spectral features of all three optical experiments dealing with the Cu(llO) surface it is obvious that the resonance at 2.1 eV is present and dominant in all data sets. The sensitivity of electronic surface states (of clean Cu(llO)) to adsorbed oxygen (and probably other adsorbates) causes in this case the optical techniques to be quite sensitive to adsorbates, enabling their use to monitor the kinetics of adsorption/desorption kinetics, for example. Since electronic surface states are quite common for a number of semiconductor surfaces, it is understandable that optical response investigations are sensitive to adsorbates especially on these surfaces. Hence they are frequently employed to study kinetic phenomena involving adsorption or thin film growth. 

S. Logothetidis, I. Alexandrou, S. Kokkou, Optimization of TiN thin film growth with in situ monitoring the effect of bias voltage and nitrogen flow rate. Surf. Coat. Technol. 

Monitoring surface structures, especially during thin-film epitaxial growth can distinguish two- and three-dimensional defects... 

Surface and thin film analysis has been used more extensively in the study of epitaxial growth of compound semiconductors where there is the additional requirement to monitor stoichiometry. Epitaxial deposition of GaAs is most frequently achieved by VPE or LPE, however, the area of most active research is MBE of GaAs and Ga Al, As. In MBE, a molecular beam of... 

Unlike other thin film deposition processes, conditions for diamond CVD have three unique features (i) high substrate temperature typically at 700-1200 °C, (ii) high gas pressure P at 20-150Torr (lTorr= 133.3 Pa), and (iii) low methane (CH4) concentration of usually 1-5% with respect to the dilution gas, hydrogen (H2). A standard temperature for diamond growth, monitored by an optical pyrometer without emissivity correction, is 800 °C. It is, however, considered that the surface temperature of the specimen exposed to the plasma is actually higher. Under these conditions, at least more than 95% of the deposited film can be crystalline diamond,... 

Boron-doped diamond (BDD) thin films were synthesized at CSEM (Neuchatel, Switzerland) by the hot filament chemical vapor deposition technique (HF CVD) on p-type, low-resistivity (l-3mQcm), single-crystal, silicon wafers (Siltronix). The temperature of the filament was between 2440 and 2560 °C and that of the substrate was monitored at 830 °C. The reactive gas was a mixture of 1% methane in hydrogen, containing trimethylboron as a boron source (1-3 ppm, with respect to H2). The reaction chamber was supplied with the gas mixture at a flow rate of 51 min giving a growth rate of 0.24 pm h for the diamond layer. The obtained diamond film has a thickness of about 1 pm ( 10%) and a resistivity of 15mQcm ( 30%). This HF CVD process produces columnar, random textured, polycrystalline films [9]. 

While we have discussed how to produce queirtz crystals by hydrothermal growth, we have not addressed the applications in which they are used. Two very important technical fields use quartz crystals. These are as frequency oscillators and as thin-film monitors. Both of these technologies take advantage of the fact that quartz can be act as a crystal oscillator Iqr applying a controlled voltage. 

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