Sketch of the discharge chamber.
Sketch of the experimental set up for the EUV irradiation of the samples. The pressure in the process chamber (krypton) is about 10−4 mbar. The distance from the source to the sample is about 30 cm.
Scanning electron microscope pictures of samples produced with 50 (left picture) and 150 cycles (right picture).
(a) Contact angle as a function of the number of cycles nc. The measurement was performed for two different plasma-on times: 8 s (squares) and 4 s (circles). (b) Gliding angle for three different values of nc: 100, 150, and 200. The plasma on time was 4 s. The volume of the water droplet was in all three cases 10 μl.
Sequence of pictures illustrating the spreading of a 1 μl water droplet on a surface treated with the argon plasma. The original sample was produced with 200 cycles and a plasma on time of 8 s.
(a) Contact angle as a function of plasma treatment time. The original samples were produced with 200 cycles and a plasma on time of 8 s. (b) Contact angle after irradiation with a UV flashlamp. The minimum contact angle in all cases is set to a value of 5° since it is not possible in our case to give more precise values.
FTIR spectra (transmission mode) of: (a) as-deposited untreated material (showing lotus effect), (b) after 60 min UV treatment of the deposit in the atmosphere (resulting in a superhydrophilic character), (c) spectra after 60 min EUV treatment of the material presented in curve (b) (see Sec. III C ) Reversibility and EUV irradiation: From superhydrophilic to superhydrophobic surfaces).
(a) XPS spectrum of an untreated sample in comparison with XPS spectra of samples treated with Ar plasma, N2 plasma , O2 plasma and irradiated with an UV flashlamp for 2 hours. (b) XPS spectra at O K edge.
NEXAFS spectrum (N K edge) of a sample that was treated with the nitrogen plasma. The characteristic features (N1-N3) can be attributed to as nitriles, C=N, and amino groups. 28,39–41
NEXAFS spectrum (O K edge) of an untreated sample and of samples treated with the nitrogen plasma, the oxygen plasma and the UV lamp, respectively. It is important to note that all spectra are normalized. Without normalization the features of the untreated spectrum would appear much less pronounced.
The ageing of originally superhydrophobic surfaces (leading to an increase of the roll off angle and a decrease of the contact angle) can be reversed by EUV irradiation under vacuum conditions.
Water droplet on a patterned surface which consists of a circular superhydrophilic area surrounded by superhydrophobic area.
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