Chapter 48: Light source sample

　　 "Xu Qiu, we are going to prepare a sample of the light source." Chen Wanqing said.
　　 "Light source?" Xu Qiu thought for a while, and said, "It's the synchrotron radiation center of Magic City."
　　 "Yes, they are also called Magic City Light Source, which is the latest generation of synchrotron radiation light source in China." Chen Wanqing said.
　　 "When should I go for the test?" Xu Qiu said.
　　 "Two days later, July 25, Friday, starting at nine o'clock, the time is 12 hours." Chen Wanqing said.
　　 "It takes 12 hours to test, so long." Xu Qiu said.
　　 "There is no way. When they allocate time, they allocate it in half a day." Chen Wanqing said.
　　 "Their light source is running 24 hours a day, isn't it a bit unlucky to test overnight, wait a minute..." Xu Qiu suddenly realized something.
　　 "We are not the hapless guys, right."
　　 "Yes, we are scheduled to start at nine o'clock in the evening." Chen Wanqing nodded.
　　 "After the test, it will be 9 o'clock in the morning on the 26th. I will take a day off. The interview will be held on the 28th. It shouldn’t be a big problem." Xu Qiu said after internal analysis:
　　 "Okay, senpai will teach me to prepare samples."
　　…………
　　 came to the laboratory, Chen Wanqing introduced:
　　"The substrate we use for the light source sample is a single crystal silicon wafer, because its background signal is easy to identify and subtract.
　　 First, you need to cut the silicon wafer into small pieces with a glass knife, and the area of ​​each piece should be as large as 2 square centimeters or more, which is roughly square. "
　　 After speaking, Chen Wanqing took out a round silicon wafer from the wafer box.
　　 Its diameter is about 15 cm, thickness is about 2-3 mm, and it is polished on one side.
　　 She took a glass knife, compared it with a straightedge, and drew a set of parallel lines about 1.5 cm apart on the unpolished side.
　　 Then, use two flat-tip tweezers to clamp the two ends of the straight line mark drawn by the glass cutter, and break them with force at the same time.
　　 In this way, a set of long silicon wafers with a width of about 1.5 cm was obtained.
　　 Then, with the help of a glass knife again, she broke the long silicon wafers into small pieces of approximately square wafers.
　　Of course, because large silicon wafers are round, there is inevitably a certain arc at the corners.
　　 After Xu Qiu learned, he did the same, took two round silicon wafers and broke them into small silicon wafers.
　　 The two got a total of more than 90 small silicon wafers, which is enough for this sample.
　　 "Next, wash and blow dry the small silicon wafers. There are special tools for cleaning the silicon wafers."
　　 Chen Wanqing brought a beaker with a plastic bracket.
　　" Put the silicon wafers neatly on the plastic holder, pour the solution, seal the beaker with aluminum foil, and then use an ultrasonic cleaner to ultrasonic.
The 　　 solutions are deionized water, acetone, and isopropanol, each of which is sonicated for 10 minutes, and finally the silicon wafer is dried with a nitrogen gun and placed in a petri dish. "
　　 "This is the same as cleaning the glass substrate, except that soapy water is not used." Xu Qiu said.
　　 "Yes, but be careful when using a nitrogen gun, silicon wafers are easier to fly off than ITO glass substrates." Chen Wanqing reminded.
　　 "Okay." Xu Qiu said: "By the way, don't Wu Feifei and Duan Yun need to make samples?"
　　"Wu Feifei’s three-dimensional perovskite material will directly deteriorate when exposed to oxygen, so it cannot be tested;
　　 Duan Yun mainly makes inorganic thermoelectric materials. He can use XRD to test in school, and he does not need to go to the light source to test. "Chen Wanqing said.
　　…………
　　 With the reminder from the senior sister, Xu Qiu didn't make a big mistake when drying the silicon wafer, only one piece was blown away.
　　 Then, he discussed with the senior sister which samples to make.
　　 P3HT, Chen Wanqing has 6 blending systems, 3 separate components, 9 kinds in total;
　　Spin coating methods include normal spin coating and spraying, a total of 2 kinds;
　　 set 2 groups of speed for each type;
　　 a total of 36 sets of conditions.
　　PTB7-TH system, 1 blend system, 2 separate components, 3 types in total.
　　 Solvent additives include no addition and 2 different volume fractions, a total of 3 types;
　　 Annealing and non-annealing, a total of 2 kinds;
　　 set 2 groups of speed for each type;
　　 a total of 36 sets of conditions.
　　 In fact, the speed has little effect on the final result, but the signal of organic samples is generally weak. In order to prevent accidents and ensure that each system can measure the signal, it is necessary to prepare as many samples as possible.
　　Because the area of ​​the silicon chip is small, the numerical number is used, from 1 to 72, Xu Qiu records the experimental conditions corresponding to the number in the experimental record book.
　　 Then, after ozone treatment, he put the dried silicon wafer into the glove box for spin coating.
　　 The spin coating operation of silicon wafers is almost the same as normal. Although the area of ​​silicon wafers is relatively small, its surface is flat and high in hardness.
　　 Therefore, only need to change a small glue spreader suction table, the silicon wafer can be firmly sucked, and it does not need to be attached to the glass to be spin-coated like a PEN substrate.
　　 Two hours later, Xu Qiu prepared all the samples and marked the number on the back of each wafer.
　　 Samples with numbers 6 and 9 need to be drawn with a horizontal line below to confirm whether it is 6 or 9.
　　…………
　　 Back to the desk, Xu Qiu did not forget to ask the senior sister for the test principle.
　　 Chen Wanqing introduced:
　　" Ordinary X-ray diffraction experiment ~EbookFREE.me~ is XRD, which is to give a crystal sample an X-ray, X-ray passing through the crystal will cause diffraction.
The diffraction signal generated by 　　 is collected by the equipment, and after data analysis, information about the arrangement of atoms in the crystal can be obtained.
　　 This kind of test has no dimensional distinction. For example, this crystal has different crystallization conditions in different directions, which cannot be seen by the XRD signal.
　　 And what we are testing is grazing incidence wide-angle X-ray diffraction, abbreviated as GIWAXS, which can be understood as a two-dimensional XRD.
　　 In other words, we can analyze the crystallization of crystals in two dimensions.
When 　　 looks like a polymer crystal, its main chain and branch chains can be crystallized, and the direction of crystallization is generally vertical.
　　 We make it into a thin film, then one dimension is the film plane, and the other dimension is out of the plane perpendicular to the film plane. The crystallization signals in the two dimensions are different.
　　 Therefore, the GIWAXS method can be used to clearly see the respective crystalline properties of the polymer main chain and branch chain, and using XRD, their signals will be mixed together and cannot be distinguished. "
　　 "Is this test difficult to do?" Xu Qiu asked: "Our general characterization can be tested in the laboratory or the public instrument platform of the school, but this has to go to Zhang Jiang."
　　 "In fact, we are pretty good, the school happens to be in the local magic city, and it only takes an hour to take a taxi to Zhangjiang.
　　 When I was testing, I met researchers from all over the country, such as the University of Hong Kong. They all came by plane one day in advance and had to book hotels.
　　 At present, there are only four synchrotron radiation sources in the country. The Modu synchrotron radiation source is the most advanced one, and it is the third-generation synchrotron radiation source. "