Fabrication and low-temperature characterization of Si-implanted thermistors

We have fabricated and characterized Si-implanted thermistors to be used as phonon sensors in very-low-temperature, single-quantum detectors. After a short review of the required thermistor properties for this type of applica tion, a detailed description of the production process and of the character ization experimental techniques is reported. The data show that the resisti vity-temperature behaviour of all of the devices follows the prediction of the variable range hopping conduction model in the investigated temperature range (4.2-0.03 K). Phonon-electron decoupling and excess low-frequency no ise show up at low temperatures, reducing the thermistor sensitivity. These phenomena are discussed and conveniently parametrized in view of a complet e detector optimization.