Final answer:
Option 4: The characteristic that is NOT true for semiconductors is that their semiconductor properties change as materials age.
Step-by-step explanation:
In answering which of the following is NOT a characteristic of semiconductors, it's important to understand the properties of semiconductors. Semiconductors, like silicon and germanium, are substances that conduct electricity better than insulators but not as well as conductors. They have intermediate resistivity, and their ability to conduct electricity can be enhanced by adding impurities, a process known as doping, which introduces free charges into the material. Semiconductor properties can also be sensitive to temperature changes. Notably, semiconductors are abundant in nature, especially silicon, which is the second most abundant element in the Earth's crust.
Based on this understanding, the statement that is NOT characteristic of semiconductors would be number 4) "Their semiconductor properties change as materials age." While the performance of semiconductor devices may degrade over time due to various factors such as thermal stress and electromigration, the intrinsic semiconductor properties themselves do not change simply due to the material aging. Instead, the number of free charges in semiconductors is strongly dependent on the type and amount of impurities and temperature, not on the age of the material.