Energy deposition rate

Fig. 3. The organic polymer 02 RIE rate (filled points) tracks the energy deposition rate (open points) as the self bias voltage is varied at 13.5 MHz and 10 mtorr (squares) or 80 mtorr (triangles).

Figure 8 Radial energy deposition rate and fraction of total energy loss in a track segment as a function of radial distance for (solid line) 1 MeV and for He ions of (OOOO) equal velocity and (x X X x) equal LET. (From Ref. 74.)...

This energy deposition rate, 4 GGy s corresponds to a temperature increase of ten million degrees per second for a thermally isolated material of specific heat 0.4 J g K Irradiation of a large piece of material at a dose rate of 1 GGy s" would result in its vaporization in a fraction of a second. Apart from transmission electron microscopes, only nearby nuclear explosions and devices that give short pulses of irradiation for the study of fast radiation processes [96] produce such high dose rates. It is important to realize that continuous irradiation in the electron microscope, even at such dose rates, does not have to cause a large rise in the temperature of the specimen. This is because a very small object like the illuminated area in a TEM has a large surface area per unit volume, and so it is efficiently cooled by thermal conduction into the rest of the specimen. 

The ionization rate is proportional to the energy deposition rate, usually a directly... 

Here C d) is a prefactor that depends on the dimensionaUty of the problem (i.e., the number of CVs included), S is the dimension of the domain to be explored, 8s is the width of the Gaussian potentials, D is the diffusion coefficient of the variable in the chosen space, and co is the energy deposition rate for the Gaussian potential. This equation has several nuances that need to be explained, and here we will do it by considering alanine dipeptide as a real-life example. 

The defects generated in ion—soHd interactions influence the kinetic processes that occur both inside and outside the cascade volume. At times long after the cascade lifetime (t > 10 s), the remaining vacancy—interstitial pairs can contribute to atomic diffusion processes. This process, commonly called radiation enhanced diffusion (RED), can be described by rate equations and an analytical approach (27). Within the cascade itself, under conditions of high defect densities, local energy depositions exceed 1 eV/atom and local kinetic processes can be described on the basis of ahquid-like diffusion formalism (28,29). 

Another disadvantage is that fragile substrates used in VLSI, such as some III-V and II-VI semiconductors materials, can be damaged by the ion bombardment from the plasma, particularly if the ion energy exceeds 20 eV. In addition, the plasma reacts strongly with the surface of the coating as it is deposited. This means that the deposition rate and often the film properties depend on the uniformity of the plasma. Areas of the substrate fully exposed will be more affected than the more sheltered ones. Finally, the equipment is generally more complicated and more expensive. 

A similar process uses a 30 cm. hollow cathode ion source with its optics masked to 10 cm. Argon is introduced to establish the discharge followed by methane in a 28/100 ratio of methane molecules to argon atoms. The energy level is 100 eV, the acceleration voltage 600 V, and the resulting deposition rate 0.5 to 0.6 im/ hour.t" ]... 

However, the nitrogen molecule has afar greater bonding energy than ammonia and is more difficult to dissociate into free atomic nitrogen active species. Consequently, the deposition rate is extremely slow. This can be offset by plasma activation with high frequency (13.56 MHz) or electron cyclotron resonance (ECR) plasmasP Ef l and with micro-wave activation. 

The discrepancy may also be caused by the approximations in the calculation of the EEDF. This EEDF is obtained by solving the two-term Boltzmann equation, assuming full relaxation during one RF period. When the RF frequency becomes comparable to the energy loss frequencies of the electrons, it is not correct to use the time-independent Boltzmann equation to calculate the EEDF [253]. The saturation of the growth rate in the model is not caused by the fact that the RF frequency approaches the momentum transfer frequency Ume [254]. That would lead to less effective power dissipation by the electrons at higher RF frequencies and thus to a smaller deposition rate at high frequencies than at lower frequencies. 

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. 

The increase in the deposition rate rj (Fig. 63d) corresponds to the increase in the ion flux (Fig. 63c) the fraction of arriving ions per deposited atom, / ,, is constant at about 0.25. Such observations have also been reported by Heintze and Zedlitz [236], who furthermore suggested that the deposition rate may well be controlled by tbe ion flux. The kinetic ion energy per deposited atom, max, is also constant and amounts to about 5 eV. As was shown in Section 1.6.2.3, the material quality as reflected in the refractive index 2 eV (Fig. 63e) and the microstructure parameter R (Fig. 63f) is good 2 cv is around 4.25, and R is low (<0.1). The depletion of the silane stays constant at a value of 4.0 0.4 seem in this frequency range. The partial pressures of silane, hydrogen, disilane (1.3 x 10 - mbar), and trisilane (2 x 10 mbar) in the plasma are also independent of frequency. Similar... 

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