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 tu...