Chapter 116: True hot spin coating

"how did you do it?"
　　 "I choose more courses for my freshman and sophomore year." Han Jiaying said:
　　 "I completed more than 60 points in the freshman semester and two, and the sophomore year added up to 50 points."
　　 "I am a ruthless man, I admire him."
　　The school stipulates that there is a maximum of 32 credits per semester.
　　 Generally, if the class selection reaches 32 points in the semester, if you listen carefully to each class and write the questions carefully after class, it is no less than rereading the third year in terms of learning intensity.
　　 Of course, with so many students in each class, there will always be a few such fierce people, but he did not expect to meet one here.
　　 In a small laboratory, two characters, Wolong and Fengchi appeared at the same time.
　　……
　　 At night, if you want to prepare a batch of devices, time is definitely not enough, unless it is in a simulation laboratory.
　　Thinking about it for a while, Xu Qiu decided to try the real-hot spin coating method first to prepare a batch of sample films and test their light absorption spectra.
　　 can not only verify whether the light absorption performance is related to the processing temperature, but also practice hand skills.
　　 Xu Qiu got up and walked into the laboratory, put on his lab coat, and entered the spin-coating glove box.
　　 seems to be followed by a small tail.
　　 glanced at the corner of her eye, it was Han Jiaying, she followed him silently.
　　 Come if you want.
　　 Xu Qiu didn't say anything, and started to check the remaining solution in the glove box.
　　P2FBT4T-2OD:PC[70]BM chlorobenzene solution prepared before, there are about 800 microliters left, but there is no need to re-formulate.
　　 Place the solution on a heating stirring table heated at 90 degrees Celsius for heating.
　　The solution is done, and the glass slides must be prepared.
　　The glass slides used in the laboratory are medical slides directly obtained from the drug warehouse. Each piece is about 7.5 cm and 2.5 cm in length and width.
　　 Before use, you need to divide it into three with a glass knife to obtain a square glass slide with a side length of about 2.5 cm.
　　 Actually, many items in the experiment are doing non-work jobs.
　　 For example, a petri dish, originally used by biological researchers to cultivate microorganisms, is now used by them to place the substrate.
　　Because a large number of square glass slides are used, Wu Feifei previously bought a workbench for cutting glass slides on Taobao, which can cut many pieces in batches at a time.
　　 Xu Qiu took the workbench with glass cutters out of the toolbox and placed it flat on the laboratory bench. On top of it, three glass slides were placed on the workbench. With three knives, nine square glass slides were obtained.
　　 just like the law, get nine pieces again.
　　 got a total of 18 pieces, which should be enough.
　　 Xu Qiu used to clean the holder and box of the substrate, and was preparing to pack the glass into the box for cleaning.
　　At this time, Han Jiaying who followed behind took the initiative:
　　 "Brother, let me help you."
　　 The sudden sound shocked Xu Qiu, and he looked back.
　　 The school girl did not know when she had already put on her lab coat and gloves.
　　 stabilized his mind, he passed the glass piece over:
　　 "This does not need to be washed with soap and water, and the ultrasound time can be shorter."
　　 Xu Qiu muttered in his heart, no wonder people want to be big brothers.
　　 It feels good to have my brother help.
　　……
　　 Around 7:30 in the evening, the others returned to the laboratory one after another.
　　 Except for Tian Qing, Duan Yun and them all arrived a few minutes earlier, only she arrived ten minutes late.
　　 Xu Qiu greeted Chen Wanqing and Han Jiaying and entered the laboratory together to prepare for spin coating.
　　 At the group meeting this week, Mr. Wei set the main theme. All experiments gave priority to Xu Qiu, so no one robbed him of the glove box.
　　 Of course, the main reason is that Wu Feifei is writing articles and has no time to experiment.
　　 Xu Qiu entered the glove box, and there were two guards beside him, guarding him.
　　 Skillfully pick up three cleaned glass sheets and place them on the heating table to heat them.
　　 This spin coating is mainly to investigate the difference between the pseudo-hot coating method and the true hot coating method, as well as the difference in the light absorption spectrum of the effective layer film at different heating temperatures.
　　 The heating temperature is set to 90 degrees Celsius and 120 degrees Celsius.
　　 Two spin coating methods, two temperatures, four conditions in total.
　　 Xu Qiu turned on the spin coater, set the parameters, and planned to try the pseudo-hot spin coating first.
　　 The operation is very smooth, no surprises.
　　 And the next real hot spin coating mainly tested his hand speed.
　　 Xu Qiu holds the pipette gun in his right hand and tweezers in his left hand.
　　 First unscrew the cap on the vial containing the solution, extend the tip of the pipette gun into the bottle, absorb the solution, keep this state but do not remove the pipette gun;
　　 Then quickly pick up a piece of glass on the heating table, transfer it to the platform of the spin coater, and then turn on the spin coater, the entire process time is controlled within 3 seconds;
　　 Then he took out the pipette gun, aimed at the glass substrate, and sprayed the solution inside it on the high-speed rotating glass plate, and the time should also be controlled within 3 seconds.
　　 Finally, cover the bottle cap of the solution bottle to prevent a large amount of solvent volatilization and cause the solution concentration to change.
　　 The whole process is smooth and flowing.
　　 The spin coating is completed within five seconds after the substrate and solution leave the heating environment, so that the temperature during the film formation process can be maintained to the greatest extent.
　　 "This operation is too fast." Han Jiaying exclaimed.
　　 Chen Wanqing was thinking that if she were to change her operation, she would definitely not be able to do this smoothly.
　　 However, in order to preserve her dignity as a senior, she was silent on the surface.
　　 The two people next to him were full of activities. Xu Qiu remained unmoved and continued the experiment.
　　 He applied two more pieces according to the experimental conditions of the two pieces just painted.
The operation of the true hot coating method is very difficult, and you must be very focused. Otherwise, if you lose your mind and there is a problem with any step of the operation, the experiment will be declared as a failure. If your solution bottle is overturned, the consequences will be even more serious.
After 　　, Xu Qiu heated the temperature of the heating table to 120 degrees Celsius, and spin-coated four samples again.
　　 A total of eight samples were obtained.
　　 "Brother, why does the spin-coated film have a circular pattern in the center?" Han Jiaying is now familiar with it and asked actively.
　　 In fact, Xu Qiu discovered this phenomenon a long time ago:
　　The hot-coated substrate has a circular pattern in the center, which is slightly smaller than the inscribed circle of the square substrate.
　　The film inside the circle is uniform, while the film outside the circle is darker, indicating that its thickness is relatively thick.
　　 But this has no effect on battery device testing, because the effective area of ​​light is in the circular area.
　　 He also discussed this question with Chen Wanqing, but did not get an answer.
　　 "I don't know the specific reason," Xu Qiu told the truth:
　　 "I infer that it is mostly caused by uneven heating of the solution during film formation.
　　The temperature of the solution and the substrate is very high, and it is difficult to maintain this temperature in an external environment at room temperature, and the temperature will gradually drop.
　　 While the solution spreads from the center of the substrate to the surroundings, then the central area will form a film first, and then the surrounding area will form a film.
　　 Assuming that the center and surrounding temperature decrease at the same rate, then the film forming temperature will be lower in the surrounding parts of the post-film formation.
　　 This may be the reason for a circular pattern in the center of the film. "
　　 "I think what the brother said is very reasonable." Han Jiaying said.
　　 "I think this is the reason too," Chen Wanqing said:
　　 "However, it doesn't make much sense to entangle this kind of problem. The problem of changing the spin coater with heating is solved."