p-Type ${\hbox{Cu}}_{x}{\hbox{O}}$ Thin-Film Transistors Produced by Thermal Oxidation

Thin-films of copper oxide
$({\hbox{Cu}}_{x}{\hbox{O}})$
were produced by thermal oxidation of metallic copper (Cu) at different temperatures (150–450
$\ ^{\circ}{\hbox{C}}$
). The films produced at temperatures of 200, 250 and 300
$\ ^{\circ}{\hbox{C}}$
showed high Hall motilities of 2.2, 1.9 and 1.6
${\hbox{cm}}^{2}\ {\hbox{V}}^{-1}{\hbox{s}}^{-1}$
, respectively. Single
${\hbox{Cu}}_{2}{\hbox{O}}$
phases were obtained at 200
$\ ^{\circ}{\hbox{C}}$
and its conversion to CuO starts at 250
$\ ^{\circ}{\hbox{C}}$
. For lower thicknesses
$\sim$
40 nm, the films oxidized at 250
$\ ^{\circ}{\hbox{C}}$
showed a complete conversion to CuO phase. Successful thin-film transistors (TFTs) were produce by thermal oxidation of a 20 nm Cu film, obtaining p-type
${\hbox{Cu}}_{2}{\hbox{O}}$
(at 200
$\ ^{\circ}{\hbox{C}}$
) and CuO (at 250
$\ ^{\circ}{\hbox{C}}$
) with On/Off ratios of
${\hbox{6}}\times {\hbox{10}}^{1}$
and
${\hbox{1}}\times {\hbox{10}}^{2}$
, respectively.