Thermal desorption spectroscopy
- Thermal desorption spectroscopy
Thermal desorption spectroscopy (TDS), also known as temperature programmed desorption (TPD) is the method of observing desorbed molecules from a surface when the surface temperature is increased. Many researchers prefer the name TPD because it is not a spectroscopic method.
When molecules comes in contact with a surface, they adsorb onto it, minimizing their energy by forming a chemical bond with the surface.The binding energy varies with the combination of the adsorbate and surface. If the surface is heated, at one point, the energy transferred to the adsorbed species will cause it to desorb. The temperature at which this happens is known as the desorption temperature. Thus TDS shows information on the binding energy.
Since TDS observes the mass of desorped molecules, it shows what molecules are adsorbed on the surface. Moreover, TDS recognizes the different adsorption conditions of the same molecule from the differences between the desorption temperatures of molecules desorping different sites at the surface, e.g. terrasses vs steps. TDS also obtains the amounts of adsorbed molecules on the surface from the intensity of the peaks of the TDS spectrum, and the total amount of adsorped species is shown by the integral of the spectrum.
To measure TDS, one needs a mass spectrometer, such as a quadrupole mass spectrometer or a time-of-flight (TOF) mass spectrometer, under ultrahigh vacuum (UHV) conditions. The amount of adsorbed molecules is counted by increasing the temperature at a heating rate of typically 2K/s-10 K/s. Several masses are simultaneously counted by the mass spectrometer, and the intensity of each mass as a function of temperature is obtained as a TDS spectrum.
The heating procedure is often controlled by a computer or a Eurotherm using a PID algorithm.
Quantitative Intrepetation of TDS data
This is usually done using the "Redhead" method [Redhead, P. A. "Thermal desorption of gases" Vacuum 12 (1962) p.203-211] , assuming the exponential prefactor and the desorption energy to be independent of the surface coverage.
References
Wikimedia Foundation.
2010.
Look at other dictionaries:
Temperatur-programmierte Desorption — Mit der Temperatur programmierten Desorption (TPD), manchmal auch thermische Desorptionsspektroskopie (TDS) genannt, kann die Bindungsenergie von Adsorbaten auf der Oberfläche untersucht werden. Inhaltsverzeichnis 1 Ablauf 2 Ergebnis 3… … Deutsch Wikipedia
J. A. Panitz — is the co inventor of the Atom Probe Field Ion Microscope [cite journal|last=Müller|first=Erwin W.|authorlink=Erwin Müller|coauthors=John A. Panitz, S. Brooks McLane|year=1968|title=The Atom Probe Field Ion Microscope|journal=Review of Scientific … Wikipedia
Ultra high vacuum — (UHV) is the vacuum regime characterised by pressures lower than about 10−7 pascal or 100 nanopascals ( 10−9 torr). UHV requires the use of special materials in creating the vacuum system, extreme cleanliness to maintain the vacuum system, and… … Wikipedia
Surface science — is the study of physical and chemical phenomena that occur at the interface of two phases, including solid liquid interfaces, solid gas interfaces, solid vacuum interfaces, and liquid gas interfaces. It includes the fields of surface chemistry… … Wikipedia
TDS — Telephone & Data Systems, Inc. (Business » AMEX Symbols) * Total Dissolved Solids (Medical » Physiology) * Total Dissolved Solids (Academic & Science » Chemistry) * Total Dissolved Solids (Academic & Science » Chemistry) * Technical Data Sheet… … Abbreviations dictionary
Catalysis — Catalyst redirects here. For other uses, see Catalyst (disambiguation). Solid heterogeneous catalysts such as in automobile catalytic converters are plated on structures designed to maximize their surface area … Wikipedia
TDS — may refer to: * (of medication) to be taken three times daily. * Total dissolved solids, the total mass content of dissolved ions and molecules or suspended microgranules in a liquid medium. * Tabular Data Stream is the name of a computer… … Wikipedia
Ernst G. Bauer — (born 1928) German American physicist. He is known for his studies in the field of surface science. His most notable contributions are his work on establishing thin film growth and nucleation mechanisms, and his invention of the low energy… … Wikipedia
Mass spectrometry — (MS) is an analytical technique that measures the mass to charge ratio of charged particles.[1] It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical… … Wikipedia
List of materials analysis methods — List of materials analysis methods: Contents: Top · 0–9 · A B C D E F G H I J K L M N O P Q R S T U V W X Y Z μSR see Muon spin spectroscopy … Wikipedia
