# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/Dd9N7ptg7jB
- **Gondola URL:** https://gondola.cc/posts/71131435-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/dafda71c31.jpg
- **Posted:** 2026-10-01T15:21:16.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Your USB drive holds data with zero power because every bit is stored as trapped electric charge inside a microscopic cage of insulation. No battery, no refresh, no moving parts. Just electrons that physically cannot escape.

The core device is the NAND flash memory cell:

• Each cell is a modified MOSFET transistor with an extra layer called a floating gate (or a charge trap layer in modern 3D NAND)
• That gate is completely surrounded by silicon dioxide, one of the best electrical insulators known
• The oxide barrier is only about 8 to 10 nanometers thick, yet electrons at room temperature lack the energy to cross it
• Charge stored there can persist for roughly 10 years or more under normal conditions

How a bit gets written:

• A high voltage (around 15 to 20 V, generated on-chip by charge pumps from the 5 V USB supply) is applied to the control gate
• This creates an electric field strong enough to let electrons quantum tunnel through the oxide, a process called Fowler-Nordheim tunneling
• Once the voltage is removed, the electrons are stranded with no path out

How a bit gets read:

• Trapped electrons shift the transistor’s threshold voltage, the voltage needed to turn it on
• The controller applies a reference voltage and checks whether current flows
• Current flows means one state, no current means the other

Packing more data per cell:

• SLC stores 1 bit per cell using 2 charge levels
• MLC stores 2 bits using 4 levels
• TLC stores 3 bits using 8 levels
• QLC stores 4 bits using 16 levels

More levels means higher density and lower cost, but the voltage windows get tighter, so error correction and wear become bigger engineering problems.

Every write and erase cycle slightly damages the oxide, which is why flash has finite endurance and why controllers spread writes across the chip with wear leveling.

#stemantics #electricalengineering #semiconductors #computerscience #stemeducation

## Stats

- **Views:** 12,651
- **Likes:** 210
- **Shares:** 0
- **Comments:** 4

## Tags

stemeducation, semiconductors, computerscience, electricalengineering, stemantics

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