OU Gu-ping, GUI Wen-ming, JIN Shi-chao, ZHANG Fu-jia. Surface and Interface Analysis of LiBq<sub>4</sub>/ITO Using Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS)[J]. Chinese Journal of Luminescence, 2005,26(3): 337-343
OU Gu-ping, GUI Wen-ming, JIN Shi-chao, ZHANG Fu-jia. Surface and Interface Analysis of LiBq<sub>4</sub>/ITO Using Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS)[J]. Chinese Journal of Luminescence, 2005,26(3): 337-343DOI:
Blue OLED is very crucial to realize full-color displays. It was harder to gain highly efficiency blue OLEDs compared with red and green OLEDs. LiBq
4
was supposed to be a newly potential blue organic light-emitting material. As the states of the interface between organic layer and electrode and the film quality of organic layer affect the properties of OLEDs
we investigated the surface and interface states of LiBq
4
/ITO by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). LiBq
4
was deposited on ITO coated glass by routine vacuum evaporation. The thickness of LiBq
4
was about 200 nm. The surface morphology of LiBq
4
was checked by AFM within a area of 8.0 μm×8.0 μm both in lateral and topographic force contact modes. XPS was introduced to study the surface and interface electronic states of LiBq
4
/ITO. The scan spectrum was analyzed and the peaks of elements were deconvoluted to further investigate the chemical states of LiBq
4
.AFM results show that the surface of LiBq
4
on ITO was very rough with many cracks and pores
indicating poor film quality of LiBq
4
on ITO. From the analysis of the XPS spectrum
we found that
the concentration of contaminated C atoms was very high in the surface of LiBq
4
/ITO
which reduced significantly in the interface. This was another proof of the existence of cracks and pores in LiBq
4
that these cracks and pores can lead to heavy absorption of gas molecules; LiBq
4
was partially oxidized showed by the emergency of an oxidizing characterized shoulder peak in the C1s spectrum; The relative concentration of B atoms reduced in the interface
which indicate that some B atoms detached from LiBq
4
and lead to the further oxidization of LiBq
4
; from the spectrum of N1s
we found that unlike the case in Alq
3
no evidence shows B atoms bonding to N atoms through coordination
which leads to blue shift of the EL spectrum of LiBq
4
. But in the interface
a new shoulder peak emerged which may be caused by N atoms bonding with In and Sn atoms came from ITO layer. It may affects the EL spectrum of LiBq