| Single-walled carbon nanotubes have excellent electrical,mechanical and optical properties,and can exhibit metallic or semiconducting properties depending on their chirality,providing a variety of possibilities for the application of carbon nanotubes in electronic devices.At the same time,layered two-dimensional materials such as graphene have ultra-thin structure and rich material categories,which has opened up a new development direction for constructing new electronic devices.Among them,the transition metal sulfide has a suitable band gap width and high carrier mobility;gallium antimonide is a direct band gap semiconductor,exhibits obvious in-plane anisotropy,and can be used to construct photoelectric sensor and multi-value memory devices based on field effect transistor structure.As one of the basic structural units of semiconductor devices,field effect transistor has many typical structures and functions.Floating gate memory is a kind of nonvolatile memory,which has the characteristics of low power consumption,fast access speed and low cost.Fin field effect transistor is developed on the basis of the structure of planar field effect transistor which is superior to the gate control capability of the planar device,and also effectively reduces the size of the device.In this paper,based on three low-dimensional materials,carbon nanotubes,gallium telluride and transition metal sulfides,we systematically studied the design,construction and performance of a new type of floating gate memory and fin field effect transistor.A method combining electrical anisotropy with layered two-dimensional material van der Waals heterojunction is developed to realize the multi-value storage function of gallium telluride floating gate memory.An aluminum nano-crystal/alumina integrated structure as floating gate layer and tunneling layer with uniform and discrete distribution semiconducting carbon nanotube films is proposed to obtain high performance flexible carbon nanotube floating gate memory.A single atomic layer transition metal sulfide fin transistor isolated vertically is obtained.The main findings are presented below.(1)The material has different lattice periodicity along different crystal directions,which makes the crystal exhibit electrical anisotropy,which is more obvious in two-dimensional materials.Using the semiconducting two-dimensional layered material gallium telluride,combined with van der Waals stacking technology and micro-nano processing technology,we use multi-layer graphene as the buried gate,a few layers of gallium telluride as the channel material,and hexagonal boron nitride as the dielectric layer to obtain the floating gate memory with large switching ratio(>107)and long storage time.In addition,by changing the gate voltage,the different memory windows of the floating gate can be obtained by the electrical anisotropy of gallium telluride in different directions,and then the multiple resistance states can be read out only by writing one operation voltage.(2)The rapid development of wearable electronic system demands the development of flexible memory,and carbon nanotubes become the ideal material for the design and construction of flexible memory.In the past,the tunneling layer of floating gate memory is usually thick metal oxide film.Due to the limitation of the mechanical properties of the oxide film,the tunneling layer will break under the condition of large bending stress,resulting in the failure of the storage function of the flexible device.We propose a direct tunneling type floating gate structure and a composite structure of carbon nanotube film,which greatly improves the flexibility and durability of the device,realizes the current switching ratio above 105 under large strain,and the storage time exceeds 108 s;at the same time,the fabricated carbon nanotube floating gate memory devices also show excellent photoelectric response and optical storage characteristics.(3)In the past 20 years,the fin width in the fin transistor vertical channel has been reduced from several hundred nanometers to the sub-ten nanometers level,however,due to the precision of lithography process,the fin width reduction in recent years encountered bottlenecks.A general method for the fabrication of finned transistors from bottom to top is presented.The channel materials of molybdenum disulfide,tungsten disulfide and semiconductive carbon nanotubes are prepared by using metal film and carbon nanotube film as gate materials respectively.The fin transistors with a minimum width of 0.6 nanofins are obtained and the device shows bipolar behavior,and the current switch ratio reaches 103,which provides a new way for further continuation of Moore’s Law. |
