Effect of outgassing on the field emission property of tetrapod ZnO

To study the mechanism of current degradation of a cold cathode, the outgassing measurement of a field emission diode with tetrapod zinc oxide (ZnO) cathode has been taken with a quadrupole mass spectrometer (QMS) in an ultra-high vacuum (UHV) system. It was found that the H2, CO2, CO, and CH4 were outgassed from the diode during the working process. The partial pressure of outgassing increases with the increased emission current density. The field emission properties of the cold cathode, such as turn-on field, threshold field and the emission current density, were largely related to the pressure of the outgases. From the outgassing experimental results, the relation between the emission current degradation and the outgassing of field emission devices has been found. Due to the outgassing, the work function of ZnO cold cathode increases, while the field enhancement factor decreases. Therefore, the outgassing plays very important role in the current degradation for the field emission devices (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)