UV/ozone cleaning

We used the UV/ozone cleaning method for the cleaning of substrates [43], An Xe excimer lamp with the wavelength 172nm (UER 20-172, Ushio Inc.) was used for the UV light source. The principle and method of the UV/ozone cleaning are described below. 

Ta20s-coated glass substrates were cleaned in an ultrasonic bath (BRANSON 3200) in 2-propanol for 15 min followed by UV/ozone cleaning (BOEKEL model 135500, Boekel Ind. Inc., PA) for 30 min. A SAM was formed by a subsequent immersion in the octadecylphosphoric acid ester solution for up to 48 h. Following immersion, the substrates were removed from the solution and rinsed with 2-propanol, blow-dried with He, and stored in air until analysis. The ODP SAM is stable for several hours in the n-heptane/2-propanol mixed solution, as well as in pure 2-propanol, and for weeks if stored in air. 

The water contact angles are typically below 10° for the flat titaniiun oxide and titanium metal surfaces when measured immediately (<5 min) after UV/ozone cleaning. 

Thin solid films of PS63-(PBLGlU37)s with an average thickness of a few tens of nanometres (as determined by ellipsometry) were obtained by spin-casting of chloroform (CHCI3) polymer solutions onto hydrophilic UV/ozone-cleaned silicon wafers. 

Fig. 7.2 XPS plots of Pt4/ of Pt nanoparticles with TTAB capping measured (a) before and (b) after 2 h of UV-ozone cleaning. The Pt (PtO) and Pf + (Pt02) oxidation peaks are represented with red and blue curves. The chemical shift of the Pt4/core level of PtO and PtO relative to pure Pt are about 1.2 and 3.0 eV. (c) Turnover rate and activation energy measured on TTAB and HOT before and after UV-ozone cleaning...

Figure 7.2 shows plots of the Pt4/peaks of tetradecyltrimethylammonium bromide (TTAB)-capped nanoparticles before and after 2 h of UV-ozone cleaning. The Pt4/7/2 core level is fitted at 70.9 eV and the chemical shifts of the Pt4/core level of the natural oxidation states (PF from PtO and PP" from Pt02) relative to pure Pt are about 1.2 and 3.0 eV. As shown in Fig. 7.2a, the Pt4/peak of bare TTAB-capped nanoparticles exhibits an oxidation state of PP. After UV-ozone cleaning, the XPS Pt4/ peak reveals higher oxidation states, which indicate the formation of PP". In accordance with the XPS results above, the turnover rate also... 

A (100) oriented p-silicon wafer (Wacker Chemitronic) was cut into 5x5 mm pieces. These were cleaned in a UV/ozone dry stripper (Samco) for 15 min followed by a two minute rinse in doubly deionized water. The samples were dried in clean air for several minutes. A 10 pi amount of TEOS (purchased by Aldrich, electronic grade, as received) was dropped onto the dried surfaces. The film was allowed to dry in ambient air for 10 minutes and then immediately transferred into the vaccum-chamber of the TOF-SIMS spectrometer. 

For the fabrication of devices, glass substrates (0.7 mm) coated with ITO (80 nm, 10-20 ohm/ square sheet resistance) were used. After routine cleaning procedures for the substrate with wet (acetone and isopropyl alcohol) and dry (UV-ozone) processes, a blended solution of organic materials was spin coated (700 rpm) on top of ITO, precoated with a poly(3,4-ethylenedioxythiophene) poly(4-styrenesulphonate) (PEDOT PSS) hole-injecting buffer layer. The basic organic solution consisted of a hole transporting material of N,N -diphenyl-... 

All substrates were ultrasonically cleaned with toluene and ethanol for 5 min. Organic residues were removed by treatment with an UV-ozone lamp for 20 min. 

For device fabrications as described in Section 5.3 and 5.5, 30 Q patterned ITO-coated glass substrate was cleaned with Decon 90, rinsed in deionized water, then dried in an oven, and finally treated in an ultraviolet (UV) ozone chamber. The OLEDs were fabricated by thermal evaporation at a vacuum of 5 X 10 7 mbar. 

For OTFT measurement, a heavily doped p-Si wafer wifh an overlayer of Si02 (300nm, Q—llnF/cm ) was used as fhe subsfrafe. The subsfrafe was cleaned sequentially using ethanol and acetone in ultrasonic bath, followed by an exposure to UV-ozone for 20 min [73]. During fhe organic film deposition, the substrate was kept at 60°C. The thickness of fhe organic layer was 100 nm. In the case of NPB, 20 nm of tungsten oxide x 2-3) was ther-... 

The cleaning protocol may include polishing, ultrasonic treatment in different solvents and solutions, plasma and UV/ozone etching, or sputtering a fresh surface from the IRE material, depending on the system under study. The surface cleanliness may be checked by comparing the ATR spectrum of the cleaned sample IRE with the spectrum of a new reference IRE. 

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