TDS Thermal Desorption Spectroscopy

With correct experimental procedure TDS is straightforward to use and has been applied extensively in basic experiments concerned with the nature of reactions between pure gases and clean solid surfaces. Most of these applications have been catalysis-related (i. e. performed on surfaces acting as models for catalysts) and TDS has always been used with other techniques, e.g. UPS, ELS, AES, and LEED. To a certain extent it is quantifiable, in that the area under a desorption peak is proportional to the number of ions of that species desorbed in that temperature range, but measurement of the area is not always easy if several processes overlap. 

In principle GD-MS is very well suited for analysis of layers, also, and all concepts developed for SNMS (Sect. 3.3) can be used to calculate the concentration-depth profile from the measured intensity-time profile by use of relative or absolute sensitivity factors [3.199]. So far, however, acceptance of this technique is hesitant compared with GD-OES. The main factors limiting wider acceptance are the greater cost of the instrument and the fact that no commercial ion source has yet been optimized for this purpose. The literature therefore contains only preliminary results from analysis of layers obtained with either modified sources of the commercial instrument [3.200, 3.201] or with homebuilt sources coupled to quadrupole [3.199], sector field [3.202], or time-of-flight instruments [3.203]. To summarize, the future success of GD-MS in this field of application strongly depends on the availability of commercial sources with adequate depth resolution comparable with that of GD-OES. 

Fast-atom Bombardment Mass Spectroscopy (FABMS) 

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While A

metal-water interactions are better probed by thermal desorption spectroscopy (TDS) in which heat is used to detach molecules from a surface. TDS data are in parallel with A (and AX) data. This is illustrated in Fig. 19.35 The spectrum of Ag(110) shows only one peak at 150 K, corresponding to ice sublimation. This means that Ag-H20 interactions are weaker than H20-H20 interactions (although they are still able to change the structure of the... 

Desorption is important both because it represents the last step in a catalytic cycle and because it is also the basis of temperature-programmed desorption (TPD), a powerful tool used to investigate the adsorption, decomposition and reaction of species on surfaces. This method is also called thermal desorption spectroscopy (TDS), or sometimes temperature programmed reaction spectroscopy, TPRS (although strictly speaking the method has nothing to do with spectroscopy). 

We have undertaken a series of experiments Involving thin film models of such powdered transition metal catalysts (13,14). In this paper we present a brief review of the results we have obtained to date Involving platinum and rhodium deposited on thin films of tltanla, the latter prepared by oxidation of a tltanliua single crystal. These systems are prepared and characterized under well-controlled conditions. We have used thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and static secondary Ion mass spectrometry (SSIMS). Our results Illustrate the power of SSIMS In understanding the processes that take place during thermal treatment of these thin films. Thermal desorption spectroscopy Is used to characterize the adsorption and desorption of small molecules, In particular, carbon monoxide. AES confirms the SSIMS results and was used to verify the surface cleanliness of the films as they were prepared. 

One of the standard surface science methods for assessing the concentration and stability of a chemisorbed species is thermal desorption spectroscopy (TDS). An early paper by Redhead ( 7) developed the conceptual framework for certain cases. Many papers since then have expanded the applicability of this method. Recent work of Madix Q8) > Weinberg (9) and Schmidt CIO) is particularly noteworthy. Most of this work focuses on the desorption of a single molecular species and not on reactions in desorbing systems. However, qualitative features of the temperature dependence of reactions can be assessed using this method. Figures 1 and 2 taken from the... 

Temperature programmed desorption (TPD) or thermal desorption spectroscopy (TDS), as it is also called, can be used on technical catalysts, but is particularly useful in surface science, where one studies the desorption of gases from single crystals and polycrystalline foils into vacuum [2]. Figure 2.9 shows a set of desorption spectra of CO from two rhodium surfaces [14]. Because TDS offers interesting opportunities to interpret desorption in terms of reaction kinetic theories, such as the transition state formalism, we will discuss TDS in somewhat more detail than would be justified from the point of view of practical catalyst characterization alone. 

Adsorption at Low Pressure (P < 10" Torr). The adsorption of propene has been studied with thermal desorption spectroscopy (TDS) on all of the different forms of the (100) and (111) surfaces and under several different conditions of exposure. For exposures at low pressure (P< 10 Torr), no selective oxidation is observed. For small exposures (< 5 L) at low-temperature (100K-120K), four propene desorption states are observed from the Ci O(lll) surface comparecf to two desorption states from the Cu9O(100)-Cii surface. These TDS results are shown in Figure 3, and give a cfear indication of a structure-sensitive interaction of propene with Cu20. 

Other temperature-programmed techniques include Temperature Programmed Oxidation and Sulfidation (TPO and TPS) for investigating oxidation and sulfidation behaviour, and Temperature Programmed Desorption (TPD) (also called Thermal Desorption Spectroscopy [TDS]), which analyses gases desorbed from the surface of a solid or a catalyst on heating. 

The same system, i.e., C2H2 on Pt(l 11) has also been studied by ultraviolet photoelectron spectroscopy (UPS), by high resolution electron energy loss spectroscopy (HREELS), and by thermal desorption spectroscopy (TDS). The authors have all... 

Temperature control in electrode kinetics, 1121 Terraces, electrodepositon, 1307, 1336 Thermal desorption spectroscopy (TDS), 787 Thermal reactions in semiconductors, definition, 1088... 

The TPD experimental technique is alternatively, but less suitably, termed thermal desorption spectroscopy (TDS). It is a very useful complement to vibrational spectroscopy and can be applied to adsorption on single-crystal or finely divided metal surfaces. TPD involves the dynamic analysis, usually by mass spectrometry, of the gases desorbed from the surface as the temperature is raised at a uniform rate, starting from a known state of adsorption. In addition to... 

Another possibility is to heat the surface up slowly and to measure the quantity of desorbed material versus the temperature. This is called temperature programmed desorption (TPD) or thermal desorption spectroscopy (TDS). Usually distinct maximums are observed which correspond to the breaking of specific bonds. 

Castro F.J., Meyer G. (2002) Thermal desorption spectroscopy (TDS) method for hydrogen desorption characterization (I) theoretical aspects, J. of Alloys and Compounds 330-332, 59-63. 

Thermal Release During Thermal Desorption Spectroscopy (TDS)... 

In order to characterize the MgO sites where the Pd atoms are stabilized after deposition by soft-landing techniques, we used CO as a probe molecule [61]. The adsorption energy, Eb, of CO has been computed and compared with results form thermal desorption spectroscopy (TDS). The vibrational modes, (o, of the adsorbed CO molecules have been determined and compared with Fourier transform infrared (FTTR) spectra. From this comparison one can propose a more realistic hypothesis on the MgO defect sites where the Pd atoms are adsorbed. 

Castro F.J., Meyer G. (2002) Thermal desorption spectroscopy (TDS) method... 

UHV-high-pressure reaction cell are preferable. Such an instrument that has been successfully applied for several years is shown in Fig. 8 (48,84,118). The UHV section (lx 10 mbar) is equipped with tools for sample preparation (Ar ion gun, metal evaporator, quartz crystal microbalance) as well as sample characterization by FEED, AES, and thermal desorption spectroscopy (TDS). After analysis of the model catalysts under UHV, the samples are transferred (still under UHV) to the SFG cell. When the manipulator is lowered to the SFG level, the sample holder is... 

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