In one aspect, a device includes a threshold switch formed of a mixture. The mixture includes at least 0.90 parts by mole of a composition of three or four chemical elements of: from 0.20 to 0.70 parts by mole of Si, from 0.05 to 0.60 parts by mole of Te, and from 0.05 to 0.60 parts by mole of S, P, or a mixture of S and P. The mixture also includes at most 0.10 parts by mole of optional other chemical elements different from Si, Te, S, and P. The parts by mole of the mixture add up to 1.00.