In the evening of that day, Carl came to Caltech, got the necessary documents from Evan to apply for a patent, and hurried away.

In order to relieve the anxiety of waiting, Evan found playing cards, glued a layer of white paper to them, and drew PWH cards on them. In less than a day, two sparring decks were made. After trying to play against Evan for a few rounds, Rick became addicted to it.

Waiting left and right, the plastic parts of Evendin were finally delivered on Thursday.

Magic7 sent someone to send it.

When he got the materials, Evan immediately threw down the cards and left them alone. It just so happened that he had already made most of the cards in the core set he remembered, and he wasn't even interested in the rest of the library and numerical balance design.

On Friday, Evan didn't show up for class and spent the whole day in the lab with Leyton.

Everything was ready, and the two in white coats began to make point contact transistors.

The structure of a point-contact transistor looks simple, but it is also a test of one's hands-on ability to make it.

First of all, they need to spread the conductive material gold leaf on a horizontal surface under the "匚" shaped plastic frame, and then put germanium single crystals on top of the gold leaf;

Then, the gold leaf is spread on one corner of the triangular wedge, and the spring is attached to the side corresponding to the corner, and in this step the two must be careful not to break the gold leaf;

Then the other end of the spring is fixed on the horizontal side above the frame of the word "匚", in order to make the spring can be adjusted up and down, so the screw is used;

Finally, the wedge with gold leaf is pressed on the surface of the germanium single crystal, under the action of pressure, the gold leaf on the corner will be broken, this step is very critical, the force exerted on the wedge can not be too large or large, it is necessary to ensure that the two sections of gold leaf are close enough together.

This point-contact transistor, Evan and Layden collaborated to make it in more than an hour. It was faster than Evan had expected.

The next step is testing, if this is a successful transistor, when a small current is added to the gold foil on one side, the gold foil on the other side will be able to measure a larger current.

In the experiment, the former is defined as the emitter and the latter as the collector.

Around this "tiny" transistor, the two turned around several times, and after confirming that there was no problem, they moved it to the experimental table. On the test bench is a measuring instrument and a power supply for experiments, which can adjust the output voltage. After placing the transistor on the measurement circuit, which had been prepared for a long time, the two began the test work in earnest.

Evan served as the tester and Leiden acted as the data logger.

At the beginning of the experiment, Evan first gave the emitter a small voltage (Ve), 0.1 volts, and then adjusted the emitter current (Ie) by adjusting the load resistance, and the measured Ie was also very small at the beginning, in the order of milliamps.

"No current (Ic) passes through the collection pole!"

Leyden glanced at the ammeter and reported.

This result is normal.

After Leyton recorded the results, Evan began to increase Ie.

"0.5 mA ......"

"IC is zero. ”

"Continue, Ie is 1 mA ......"

"IC is zero ......"

Ie is added until it can no longer be added (the load resistance has been adjusted to the minimum), and the Ic does not respond.

Evan and Layton looked at each other, both feeling a bad premonition.

Evan proposes: "Add Ve ......"

Layton nodded and said, "How about I add Ve directly to 0.5 volts?"

“OK！”

Evan twisted the adjustment knob of the power supply, set the output voltage to 0.5 volts, re-increased the load resistance, and the test restarted.

"Ie, 0.4 mA ......"

"Ic, zero. ”

"Ie, 1 mA ......"

"Ic, zero. ”

Evan frowned, and instead of increasing Ie little by little, he increased it to the maximum at once.

"Ie, 3.6 mAh...... IC, zero"

Seeing this result, the expression on Evan's face became heavier and heavier.

Even so, though, testing continues.

About half an hour later, the scheduled test was over, and Layton sat gloomily in a chair on the edge of the bench, with the experiment log sheet in his hand, his eyes revolving between the experimental data and the transistors on the bench.

Evan spread his legs, his left and right elbows propped up on his thighs, his palms crossed with his fingers crossed, his upper body leaned forward and bowed, his fingertips pushing his chin from time to time, and his face was pensive.

It is clear that this transistor failed.

Both were reviewing what went wrong.

It was already past twelve o'clock, but neither of them had any intention of going to lunch.

After a period of contemplation, Evan was the first to break the silence and said, "Leyden, first of all, we must have a consensus, that is, the theory I first premised is correct......"

Layton put down the record sheet, nodded at Evan, and said, "I agree!"

"Good!" Evan straightened up, pointed to the transistor on the bench, and said, "Well, that's the problem." ”

"The first possibility, the problem of germanium crystalline materials, according to Bardeen's paper, is that the purer the material, the better...... Bell Labs may have been on the defensive side. ”

Layton said: "It's possible, but I think it's a little less likely......"

"That's right!" Evan stood up suddenly, propped his hands on the edge of the test table, stared at the transistor intently, and said, "It's more likely that we didn't do a good job somewhere......"

Layton stood beside Evan, clasped his arms in his arms and whispered, "Where is it? Where ......is it?"

Suddenly, he paused, and a flash of inspiration flashed in his mind, and almost at the same time, Evan turned around.

The two glanced at each other and said in unison, "Width!"

Seeing that the other party and himself thought together, the two looked at each other.

"Yes, before I made this transistor, I mentioned that the width between the two gold leaf contacts was the key, and now I think I'm taking it lightly," Evan says. ”

"So, how about we take it apart and measure the width between the contacts?"

Layton was about to nod his head when his stomach suddenly growled.

Evan smiled and said, "Forget it, let's solve the stomach problem first!"

Solving lunch as fast as they could, the two couldn't wait to dive headlong into the lab.

After a cursory measurement, Evan found that the distance between the two pieces of gold leaf was more than 0.5mm.

"This span is too long, it must be reduced to less than 0.25mm!"

Finding the reason, Evan breathed a sigh of relief.

However, now the question also comes, how to ensure that the width meets the requirements?

Reducing the force when the wedge is pressed down while crafting is the easiest way to do this, but it takes a bit of luck.

Evan and Layton decided to try a few times first, and if that didn't work, then talk.

Evan thinks that a few more attempts will always succeed, after all, there is already a "precedent".

However, after an afternoon and a night, the two wasted many pieces of gold leaf, and still did not succeed.

The two of them, who were depressed and looked "non-" with a "non" face, could only fight again another day.