I Have a Research Support System

Text 392 It's time to dedicate ourselves to science (for subscription)

After the vacuum of the vapor deposition chamber reached the standard, Xu Qiu and Mo Wenlin returned to the laboratory and first vaporized molybdenum trioxide using the beam source furnace heating method according to the normal method.

After that, wait for the temperature of the beam source furnace to drop below 100 degrees Celsius, and begin preparations for vapor deposition of metal electrodes.

Usually when evaporating thick-film metal electrodes, the evaporation rate is not very important. Sometimes in a hurry, the electrode will be prepared directly by flash evaporation.

The so-called flash vaporization, highlighting the word "flash", is to directly use a large current, under the premise of not blowing the fuse, the vapor deposition rate is fully extended, and the film is plated with a swish.

In contrast, the normal vapor deposition rate of a metal electrode is about 1 angstrom per second, that is, the vapor deposition rate of 0.1 nanometers per second, and it takes about 17 minutes to vaporize 100 nanometers.

The flash rate may reach 6 angstroms per second, or even more than 10 angstroms per second, which can be done in just a few minutes.

In addition to the fast steaming, flash evaporation has another advantage, that is, the thickness of the steam and the high utilization rate of the target.

Especially when evaporating gold, because gold is more expensive, in order to prevent wastage, the gold target is added as little as possible and then flashed directly.

According to Xu Qiu's experience, if the gold film thickness obtained by flash evaporation is 100 nanometers, the thickness obtained by normal rate evaporation may be only 30-50 nanometers, and the gap is still very large.

All things have advantages and disadvantages, and flash evaporation also has disadvantages, that is, the film obtained by evaporation becomes uneven.

To give an example that is not very vivid, imagine the process of vapor deposition as the process of hail. The surface of the device can be imagined as a soil surface. The faster the evaporation rate, the larger the hail particles and the faster the falling speed, the easier it is to give the ground to the ground. Hit the pit.

Corresponding to the manifestation of the evaporation process, that is, the faster the evaporation rate, the more the target molecules tend to penetrate the effective layer or the transmission layer film, thereby forming metal electrodes with different thicknesses at different positions.

When the total thickness of the metal electrode is relatively thick, the uneven thickness has little effect. Assuming that the film thickness is 100 nanometers and the thickness deviation is 10 nanometers, the final thickness distribution will also be 100 ± 10 nanometers, which will naturally not affect Conductivity to the electrode.

But if the thickness is relatively thin, this effect will be obvious, the thickness is 10 ± 10 nanometers, and some places will be directly disconnected.

Therefore, in order to ensure the continuity of the electrode, in order to ensure the continuity of the electrode, not only the flash evaporation is not allowed, but the evaporation rate must be further reduced.

The evaporation rate Xu Qiu plans to choose is about 0.2 angstroms per second, which is equivalent to the rate of evaporation of the molybdenum trioxide transport layer. It takes about 1 minute to vaporize 1 nanometer of gold, and about 7 and a half minutes for 9 nanometers of silver. , The time for evaporation is shorter than usual.

The theory is reasonable and practice begins.

Xu Qiu set up various parameters of the gold target, including density, z-factor, etc., and then activated the current heating device to adjust the current output terminal to the loop of the gold target, and at the same time instructed Mo Wenlin:

"Mo Wenlin, please record the experimental conditions. Just now, the molybdenum trioxide is 565 degrees Celsius, 0.2-0.3 angstroms per second, and the film thickness is 10 nanometers. The next gold and silver electrode film thicknesses are 1 nanometer and 9 nanometers, respectively. The evaporation rate is 0.2 angstroms per second..."

"Okay." Mo Wenlin nodded, and then took out an experiment notebook from the top of the evaporation glove box and started recording.

The use of large-scale instruments like this needs to be recorded. It is easier to be held accountable if there is a problem. Of course, it is not entirely for the purpose of accountability. This will also prevent the experimenters from forgetting the previous experimental conditions.

Especially for unskilled newcomers, if they forget the experimental conditions and there is no elderly person nearby to consult, they can flip through the previously recorded conditions and imitate them.

Xu Qiu turned the **** and slowly increased the current intensity from 0 amps to 5 amps, then to 10 amps, and then to 15 amps.

During this process, the real-time vapor deposition rate displayed by the film thickness meter is all beating back and forth between ±0.01 angstroms per second, and the fluctuation range is small.

This is mainly because the density of gold is relatively large. When the film thickness meter uses the electrical signal on the crystal oscillator to convert the evaporation rate, the density is on the denominator, so the error caused by airflow disturbances will become smaller.

At 15 amps, Xu Qiu stabilized the current and stayed there for a few minutes.

This step is dictated by habit, and the purpose is to preheat and raise the temperature of the tungsten wire and the target first.

This step is very useful when evaporating aluminum. On the one hand, it can prevent the evaporation rate from being uncontrolled. On the other hand, if preheating is not performed, it may cause the aluminum bar hanging on the spiral tungsten wire to fall, or even tungsten. The wire fuses directly, causing the experiment to fail.

Although it is not a spiral tungsten wire but a tungsten basket when evaporating gold and silver, it does not hurt to be careful.

Xu Qiu continued to increase the current until 17.5 amperes. The evaporation rate jumped from 0.01 to 0.01 upwards from ±0.01 angstroms per second, and the current value also began to fluctuate, indicating that the gold target had begun to melt.

After waiting for a few seconds, the evaporation rate reached 0.10 angstroms per second, and gradually stabilized.

Without hesitation, Xu Qiu directly pressed the reset button of the film thickness meter and the button of the sample baffle at the same time to start evaporation.

Then, he operated the current control **** with one hand and placed one hand on the sample baffle. His eyes were always on the evaporation rate and film thickness, and he planned to stop at any time. After all, he had to evaporate 1 nanometer of gold, which is only 10 angstroms. .

"Xu Qiu, don't you need to continue to increase the evaporation rate? Didn't you just say that the rate should be adjusted to 0.2 angstroms per second?" Mo Wenlin asked curiously. She has been in the research group for more than a month, but she has never evaporated. For gold electrodes, the electrode materials that are usually contacted are either aluminum or silver.

This is because of the device structure of the molybdenum trioxide transmission layer in the organic photovoltaic field. The three electrodes of gold, silver, and aluminum have little effect on the performance of the device, so cheap silver or aluminum is generally used.

For the perovskite system, if a spiro transmission layer is used, it usually needs to be matched with a gold electrode. The gold target purchased in the group is mainly used for the perovskite system.

"The ideal is to achieve a rate of 0.2 angstroms per second before evaporation, but in the specific experiment process, we must be flexible. Now the conditions of 0.10 angstroms per second are stable. If we force the pursuit of the expected conditions of 0.2 angstroms per second , If one is not well controlled, it may flash directly.” Xu Qiu explained:

"There is no turning back for gold vapor deposition, because the material is limited. Once the rate goes up, it is impossible to wait for the rate to fall back because the gold target may have been consumed by then, so I can only bite the bullet and steam it."

"That's it." Mo Wenlin nodded.

Xu Qiu kept adjusting the current to keep the evaporation rate at 0.1-0.2 angstroms per second.

After more than a minute, the value displayed by the film thickness meter finally jumped from 9 angstroms to 10 angstroms. Xu Qiu immediately closed the sample baffle, and then slowly reduced the evaporation current until its value decreased to 0.

After the deposition of the gold film was completed, Xu Qiu finally felt relieved. He was not worried that the gold would not be enough, because he had already experimented in a simulation laboratory before, mainly for fear of unexpected events such as uncontrolled deposition rate.

Next, Xu Qiu adjusted the current output terminal to the loop of the silver target and set the silver parameters in the film thickness meter.

The difficulty of vapor deposition of silver electrode is relatively small, because the amount of target material added is enough, there is no need to worry about the problem of excessively high vapor deposition rate, the big deal is to directly reduce the current and reheat it.

There was no accident in this step. Xu Qiu smoothly vaporized the silver electrode at a rate of 0.1-0.2 angstroms per second, and then turned his head and asked, "Mo Wenlin, have you lost your studies?"

"Studies are abolished." Mo Wenlin thought for a moment and replied: "The current should be slowly increased, and the evaporation rate should be stable at 0.1-0.2 angstroms per second, and the gold target should be vaporized once. The plating is complete."

"Well, the summary is not bad." Xu Qiu nodded, then raised his finger to the evaporation chamber.

Mo Wenlin understood, walked to the glove box vapor deposition chamber, twisted the nitrogen valve to start deflation.

After more than half a minute, the vapor deposition hatch made a "duang" sound and the hatch opened.

Close the nitrogen valve, Mo Wenlin enters the glove box, takes out the eight vapor-deposited devices, and places them in a petri dish.

Then, she took a piece of 1# device with tweezers, took it and observed it for a while, and said:

"It's really a translucent device, and you can see the things behind it through the device. It's just such a thin layer of electrodes, can it really conduct electricity?"

"Try it and you will know. By the way, remember to test two sets of data, one is front lighting, and the other is back lighting." Xu Qiucheng is on his chest, and he believes that his control is perfect. , As long as it is not a problem during the spin-coating process before Mo Wenlin, it is basically relatively stable.

"Okay." Mo Wenlin nodded and started testing.

The 1# system is the pce10:-4f system ~www.ltnovel.com~ The front lighting efficiency is the highest 9.03%, and the back lighting efficiency is the highest 5.24%. This result is basically the same as the result obtained by Xu Qiu in the simulation laboratory before.

"The efficiency of 9% is not bad." Mo Wenlin said with a smile, and then began to think: "How to optimize..."

After a while, Mo Wenlin suddenly thought of something, turned her head and asked: "Xu Qiu, shouldn't we prepare devices with different electrode thicknesses..."

"Binggo~" Xu Qiu nodded: "I plan to prepare translucent devices with thicknesses of 10, 12, 14, 16, 18, and 20 nanometers."

Mo Wenlin was stunned, and said pitifully: "That's not to make at least 30 batches of devices..."

"With the addition of 100-nanometer opaque devices, there will be more than 35 batches." Xu Qiu said old-fashioned: "The time has come to dedicate myself to science. Comrades, I am optimistic about you."

Mo Wenlin still looked pitiful, looking at Xu Qiu with wide eyes.

Xu Qiu couldn't help it: "I'll go to Teacher Wei and fight for you to have a unity."

Mo Wenlin suddenly changed her appearance, and said cheerfully: "Ok, it's a deal, promise to be dedicated."

Xu Qiu shook his head. As expected, the girls' acting skills are all max.

However, it doesn't matter if he surrendered a common one. Anyway, he has a big family and a big cause. This article is not bad. Even if it is a common one, he is on it. He posted a section of the article and the system admits it.

Moreover, Xu Qiu can also understand Mo Wenlin, coming here as a joint training, the external environment is very unfriendly to her, the difficulty of rubbing articles is very high, and naturally I can rub one article.

ps: Happy New Year's Eve everyone~

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