WEBVTT
Kind: captions
Language: en

00:00:00.140 --> 00:00:06.480
Well, today we're "digging" into spintronic
tunneling with Daniela at NVE.

00:00:06.480 --> 00:00:10.740
So, Danno, what is tunneling and how does it work?

00:00:10.960 --> 00:00:16.420
Tunneling is a nano-scale phenomenon where,
under the right conditions, electrons can

00:00:16.420 --> 00:00:22.740
tunnel through very thin, normally insulating
materials, causing lower resistance.

00:00:22.980 --> 00:00:28.860
Structures are called Magnetic Tunnel Junctions,
or Tunneling Magnetoresistors.

00:00:28.860 --> 00:00:31.080
Let's look at one.

00:00:32.360 --> 00:00:38.220
The section on the right is called the "free layer," because its electron spins are free to change,

00:00:38.220 --> 00:00:42.500
and the layer on the left is the “pinned,”
or reference layer, because

00:00:42.500 --> 00:00:48.360
its spin orientation is fixed
when the device is made.

00:00:48.660 --> 00:00:51.440
The barrier between the pinned and free layers

00:00:51.440 --> 00:00:54.060
is thin enough that electrons can tunnel through,

00:00:54.060 --> 00:00:56.680
As the meter shows,
because of the scattering

00:00:56.680 --> 00:00:59.540
caused by electrons
spinning in opposite directions

00:00:59.540 --> 00:01:03.160
the tunnel barrier is close to
its insulating state.

00:01:03.360 --> 00:01:07.480
When a field is applied, the free-layer polarization switches,

00:01:07.480 --> 00:01:10.200
electrons can tunnel,
and the resistance is low,

00:01:10.200 --> 00:01:15.100
even though this is
a normally insulating material.

00:01:15.460 --> 00:01:24.520
In this way we can turn the esoteric property
of electron spin into something useful: resistance.

00:01:24.960 --> 00:01:29.280
The resistance change can be very large.
Large signals can mean:

00:01:29.280 --> 00:01:32.540
smaller size, 
more precision, and 
lower power

00:01:32.540 --> 00:01:36.560
spintronic devices.

00:01:36.740 --> 00:01:42.260
Here's an SEM of an actual tunnel junction
made here at NVE.

00:01:43.360 --> 00:01:49.000
This white stripe is an aluminum-oxide tunnel barrier—eight atoms thick.

00:01:49.000 --> 00:01:54.600
This is probably magnified nearly a million times on your screen, so an eight-inch wafer

00:01:54.600 --> 00:01:57.520
would appear a hundred miles in diameter.

00:01:57.880 --> 00:02:04.860
Cool. How can our viewers "burrow" into this?

00:02:04.860 --> 00:02:08.100
You can go to nve.com for lots more info.