Measuring deposition rate

With advances in AFM, in situ imaging has become easier and more accessible, with many techniques available for imaging the deposition of macromolecules in real time. Probably it would not be difficult to conduct a thorough in situ study of deposition kinetics on dsDNA or DNA-SWCNTs. Unfortunately, to our knowledge such a study has not been undertaken. One reason is that perhaps the final density of objects observed on the surface after molecular combing is reduced by the combing process, and it is more relevant to 

DNA-SWCNTs at a low concentration of 1 pg/mL were incubated on a surface treated with chlorodimethyloctyl silane. This treatment creates a SAM of alkene chains on the surface. It favors the deposition of negatively charged DNA and DNA-SWCNTs on the surface by reducing the number of ionisable siloxane groups. This process also creates the highly hydrophobic, low-hysteresis surface necessary to avoid evaporation at the meniscus and to allow molecular combing to take place. Note that molecular combing has been demonstrated on clean, hydrophilic mica, but the set of conditions was very narrow.  

---

To evaluate each rate expression appearing in Table 3, the values of the a, c, and n were varied to obtain a minimum in the square of the relative error between the theoretically predicted and experimentally measured deposition rates. The results of this nonlinear regression analysis are presented in Table 4. It can be seen that only for Models 3 and 4 is d smaller than the errors in the measurements, +9.5% . 

A convenient way to illustrate the behavior of the model for the example of ZnS deposition is to plot the measured deposition rate, r(d, ZnS), as a function of the incident-flux rate of one element when the incident-flux rate of the second element is fixed. An example is shown in Figure 13 for the deposition of ZnS as a function of the incident-flux rate of sulfur at a substrate temperature of 200 °C. Experimental data points and curves representing the best-fit model predictions are shown for each of four zinc incident-flux rates. A nonlinear least-square procedure was used to obtain the following values for the model parameters that best fit equation 40 to the experimental data 8(Zn) = 0.6-0.7, 8(S) = 0.5-0.7, and K(ZnS) > 1015 cm2-s/ZnS. 

The measured deposition rates were normalized to the ambient concentrations of total aerosol loading to calculate deposition velocities. Calculations were made using total and fogwater loadings. We use notations ... 

Using the first approach, the trace-metal fluxes calculated for the salt marsh are compared to measured deposition rates for other sites in Table XVI. These sites were selected to represent circumstances that would be expected to yield fluxes of comparable magnitude, as well as establish reasonable limits to be expected. The station on Hawaii receives deposition from air masses that have presumably been scavenged over the ocean of most of their pollution burden, whereas the large fluxes measured... 

Nitrogen compounds, in the form of NOj, also tend to accelerate atmospheric attack. NOj, emission, largely from combustion processes, has been reported to have increased relative to SO2 levels. However, measured deposition rates of these nitrogen compounds have been significantly lower than those for SO2, which probably accounts for the generally lower importance assigned to these. 

Thus, the results shown in Figure 11.10 furnish direct support for the heterogeneity hypothesis often used to interpret colloid particle deposition kinetics under a barrier-controlled deposition regime [73]. In these experiments, particle deposition kinetics were determined as a function of salt concentration added to reduce the electrostatic energy barrier. Measured deposition rates were found by orders of... 

Dielectric Film Deposition. Dielectric films are found in all VLSI circuits to provide insulation between conducting layers, as diffusion and ion implantation (qv) masks, for diffusion from doped oxides, to cap doped films to prevent outdiffusion, and for passivating devices as a measure of protection against external contamination, moisture, and scratches. Properties that define the nature and function of dielectric films are the dielectric constant, the process temperature, and specific fabrication characteristics such as step coverage, gap-filling capabihties, density stress, contamination, thickness uniformity, deposition rate, and moisture resistance (2). Several processes are used to deposit dielectric films including atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), or plasma-enhanced CVD (PECVD) (see Plasma technology). 

Fluxes of HNO3 and HONO were measured by the flux-gradient technique, yielding 19 separate estimates of the fluxes. The mean deposition rate for HNO3 was 5.5 ng Nm s and all the observed fluxes were towards the ground. For... 

The ash eontent of liquid fuels is important in eonneetion with eleanliness, eorrosion, and deposition eharaeteristies of the fuel. Ash is the material remaining after eombustion. Ash is present in two forms (1) as solid partieles eorresponding to that material ealled sediment, and (2) as oil or water soluble traees of metallie elements. As mentioned earlier, sediment is a measure of eleanliness. The eorrosivity of a fuel is related to the amount of various traee elements in the fuel ash. Certain high-ash fuels tend to be very eorrosive. Finally, sinee ash is the fuel element remaining after eombustion, the deposition rate is direetly related to the ash eontent of the fuel. 

Dust fall The deposit rate of grits and dusts collected from the air in a measuring instrument. 

Experiments of propane pyrolysis were carried out using a thin tubular CVD reactor as shown in Fig. 1 [4]. The inner diameter and heating length of the tube were 4.8 mm and 30 cm, respectively. Temperature was around 1000°C. Propane pressure was 0.1-6.7 kPa. Total pressure was 6.7 kPa. Helium was used as carrier gas. The product gas was analyzed by gas chromatography and the carbon deposition rate was calculated from the film thickness measured by electron microscopy. The effects of the residence time and the temperature... 

The experimentally found linear increase of the deposition rate as a function of frequency is not seen in the modeling results that show saturation see Figure 18b. The linear increase has also been measured by others [119,120,249], up to an RF frequency of 100 MHz. Howling et al. [250] have measured this linear relationship, while taking special care that the effective power is independent of frequency. 

In the ASTER reactor deposition experiments were performed in order to compare with the 2D model results. Normalized deposition rates are plotted in Figure 22 as a function of radial position for data taken at 25 and 18 Pa. The deposition takes place on a square glass plate. For each pressure two profile measurements were performed, each profile perpendicular to the other (a and b in Fig. 22). A clear discrepancy is present. The use of the simplified deposition model is an explanation for this. Another recent 2D fluid model also shows discrepancies between the measured and calculated deposition rate [257], which are attributed to the relative simplicity of the deposition model. 

FIG. 22. Normalized deposition rate at the grounded electrode of the 2D model compared with experiments. Discharge settings for the model are a total pressure of 20 Pa. a power of 5 W, and an RF frequency of 50 MHz. The experiments were performed al 18 and 25 Pa. The measurements were done for two perpendicular directions, a and b. (From G. J. Nienhuis. Ph.D. Thesis, Universiteit Utrecht, Utrecht, the Netherlands, 1998. with permission.)... 

The gas flow rate is usually presented as a deposition parameter however, it is much more instructive to report the gas residence time [6], which is determined from the flow rate and the geometry of the system. The residence time is a measure of the probability of a molecule to be incorporated into the film. The gas depletion, which is determined by the residence time, is a critical parameter for deposition. At high flow rates, and thus low residence times and low depletion [303], the deposition rate is increased [357, 365] (see Figure 39) and better film quality is obtained, as is deduced from low microstructure parameter values [366],... 

Consequently the photoresponse tTph/deposition rate as about lO exp(Frf). Activation energies amounted typically to 0.7-1.0 eV. From thermally stimulated conductivity (TSC) measurements [489-492] a midgap density of states (DOS) of 1.5 x lO cm eV is determined. The product/zr at 300 K is 9 X 10 cm V . Both DOS and /rr are independent of frequency. 

FIG. 66. Effects of modulating the RF excitation frequency (a) deposition rate and average light intensity as a function of the modulation frequency, with the deposition rate at cw conditions indicated by the dotted line, (b) measured spectrally integrated emission and calculated production of SiH3 radicals as a function of time, at a modulation frequency of 50 kHz and a 509f duty cycle. [From A. C. W. Biebericher. J, Bezemer. W. F. van der Weg, and W. J. Goedheer, Appl. Phys. Lett. 76, 2002 (2000), 2000, American Institute of Physics, w ith permission.]... 

---