IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Organic Films and Devices Thursday Sessions
       Session OF+TF-ThP

Paper OF+TF-ThP14
Surface Freezing and Self-ordering Phenomena of Long Chain n-Alkanes Studied by Newly Developed High Vacuum DTA Apparatus

Thursday, November 1, 2001, 5:30 pm, Room 134/135

Session: Aspects of Organic Films Poster Session
Presenter: Y. Ouchi, Nagoya University, Japan
Authors: Y. Ouchi, Nagoya University, Japan
Y. Yamamoto, Nagoya Institute of Technology, Japan
M. Kuroi, Nagoya University, Japan
N. Yamaguchi, Nagoya University, Japan
H. Ishii, Nagoya University, Japan
K. Seki, Nagoya University, Japan
Correspondent: Click to Email
We developed a new apparatus of differential thermal analysis (DTA) capable of simultaneous measurement of UPS, XPS, NEXAFS etc to investigate phase transitions of ultra-thin films of organic molecular systems. The apparatus is installed in a high vacuum chamber for thermal isolation and measurements of photoelectron emission. The performance of the apparatus was examined using a 650 Å-thick pentacontane (n-C@sub 50@H@sub 102@) film, which may exhibit a unique monolayer phase transition at air (vacuum)/liquid interface, known as a surface freezing self-organization effect. We observed two anomalies of DTA curve around the bulk melting temperature, one of which is apparently due to thebulk melting. Since the temperature dependence of the surface specific UV photoemission measurements showed corresponding changes in photoemission current, we could conclude that the other phase transition peak originates from the formation of frozen (crystallized) single molecular layer located at the top alkane liquid surface. We will report the detailed analysis on the transition entropy and the chain length dependence of the temperature region of the existence of this unique surface freezing layer up to n=72. Though it was believed from grazing X-ray reflection measurements that the effect will disappear around n=60, our DTA system could confirm their existence over n=60. This demonstrates that our DTA apparatus is sufficiently sensitive to examine the 2D phase transitions of monolayers. Simultaneous measurement with other photoelectron emission measurement will be beneficial for the investigation of temperature dependence of organic thin films and its self-organization process.