However, one important feature of semiconductors (and some insulators, known as semi-insulators) is that their conductivity can be increased and controlled by doping with impurities and gating with electric fields. For the purposes of electric current, this combination of the full valence band, minus the electron, can be converted into a picture of a completely empty band containing a positively charged particle that moves in the same way as the electron.

These compounds share with better-known semiconductors the properties of intermediate conductivity and a rapid variation of conductivity with temperature, as well as occasional negative resistance. The first book by Laura Ingalls Wilder about her life on the American frontier, Little House in the Big Woods appeared in 1932. Widely considered the first modern children's book, A Little Pretty Pocket-Book was the first children's publication aimed at giving enjoyment to children, [28] containing a mixture of rhymes, picture stories and games for pleasure.x–xi The earliest of these books were educational books, books on conduct, and simple ABCs—often decorated with animals, plants, and anthropomorphic letters. Philippa Pearce's Tom's Midnight Garden (1958) has Tom opening the garden door at night and entering into a different age. Enid Blyton's books have been among the world's bestsellers since the 1930s, selling more than 600 million copies. The electrons do not stay indefinitely (due to the natural thermal recombination) but they can move around for some time.

and his clever ploy of introducing additional titles and products into the body of his children's books. In 1990 came General Anthology of Modern Children's Literature of China, a fifteen-volume anthology of children's literature since the 1920s. The materials chosen as suitable dopants depend on the atomic properties of both the dopant and the material to be doped.Roy of the Rovers, an immensely popular comic strip featuring Roy Race, a striker for the fictional football team Melchester Rovers, first appeared in the Tiger in 1954.