Christian Pflitsch

Light emitting diode excitation of Cr3+:Al2O3 as thermographic phosphor: experiments and measurement strategy

Light emitting diode (LED) excitation of thermographic phosphors for temperature measurements was investigated in the present work. A near-UV and a green LED excited the phosphorescence of sol?gel deposited chromium-doped alumina (Cr3+:Al2O3, ruby) on silicon in different experiments. The influence of the pulse length on signal intensity was measured and is discussed theoretically. From this, measurement strategies are recommended in order to obtain high signal levels. The temperature-dependent phosphorescence between room temperature and 800 K is compared to previously obtained laser excited phosphorescence. The phosphorescence decay time of the ruby films is found to be slightly dependent on the excitation pulse duration but neither on the excitation wavelength nor on the oxygen partial pressure in the atmosphere. In many situations the less expensive LED excitation appears to be a good alternative to the laser excitation methods. In addition, a strategy is proposed for measuring two-dimensional surface temperatures using two gated cameras; the validity was proven for pointwise measurements.

Growth of Thin Iron Oxide Films on Si ( 100 ) by MOCVD

The deposition of thin iron oxide films on Si(100) by metallorganic chemical vapor deposition at 55 mbar was systematically studied as a function of temperature between 673 and 1023 K. Ferrocene and oxygen were used as precursors. The growth rate was measured as a function of temperature and the films were characterized by X-ray diffraction (XRD), Auger electron spectroscopy, energy dispersive X-ray analysis, and scanning electron microscopy. The change from the kinetically controlled regime to the transport controlled regime occurs near 750 K. At similar temperatures, a phase change of the deposited material was observed. Films prepared at temperatures higher than 823 K show the structure of α-Fe 2 O 3 , whereas deposition at lower temperature leads to the growth of α-Fe 2 O 3 and other oxide phases. The XRD pattern of these films can be explained by the coexistence of different iron oxide phases, namely α-Fe 2 O 3 , γ-Fe 2 O 3 , and/or β-Fe 2 O 3 .

Dy3+:Al2O3 and (Dy3++Cr3+): Al2O3 Films for Temperature Sensor Applications Derived by Thermal CVD and Sol-Gel Techniques

Optical surface temperature measurements can be accomplished using thermographic phosphors (TP). These TPs can be deposited using CVD or sol-gel techniques, both techniques not being used often for this purpose. In this work dysprosium doped alumina films α-Al2O3:Dy and alumina films co-doped with dysprosium and chromium α-Al2O3:M (M:=Dy3+, Cr3+) were prepared by both techniques for TP applications and the results were compared. Diketonates of Dy, Cr and Al were used for film preparation. The phosphorescence decay lifetime of the Dy3+-transitions show strong temperature dependency in a temperature range from 1100 to 1500 K while the phosphorescence lifetime of Cr3+:Al2O3 (ruby) varies sufficiently in the temperature range from 298 up to 800 K. Thus, Cr3+-doped Al2O3 films are useful as thermographic phosphor coating for lower temperatures than Dy3+-doped films, while, co-doped films are temperature sensitive in the full temperature range from 298 up to 1500 K.

Rapid Thermal (RT) MOCVD of Undoped and Al Doped ZnO Thin Films

Zinc oxide is among different metal oxides, which can be used as transparent conducting oxide (TCO). Therefore, it is interesting for many applications, such as electrical contacts in solar cells, etc. In the present study, undoped and aluminum doped zinc oxide thin films were deposited on Si (100) and borosilicate glass substrates by using RTMOCVD and Sol-Gel techniques. In case of the RTMOCVD-process, the films were deposited using acetylacetonate of zinc and aluminum as precursors in the presence of oxygen. Tungsten lamps were used as substrate heater.

Chemische Gasphaseninfiltration von Aktivkohle mit Tetramethylsilan zur Erzeugung neuer Adsorbentien

V1.01 Chemische Gasphaseninfiltration von Aktivkohle mit Tetramethylsilan zur Erzeugung neuer Adsorbentien Priv.-Doz. Dr. C. Pflitsch (E-Mail: christian.pflitsch@uni-due.de), Dipl.-Ing. B. Curdts, Dipl.-Ing. M. Helmich, Dr. C. Pasel, Prof. Dr.-Ing. D. Bathen, Prof. Dr. B. Atakan Universitat Duisburg-Essen, Fakultat fur Ingenieurwissenschaft, Thermodynamik und CeNIDE, IVG, Lotharstrase 1, D-47057 Duisburg, Germany Universitat Duisburg-Essen, Fakultat fur Ingenieurwissenschaft, Thermische Verfahrenstechnik, Lotharstrase 1, D-47057 Duisburg, Germany DOI: 10.1002/cite.201250715