【作者】 熊志；

【导师】 顾德恩；

【作者基本信息】 电子科技大学 ， 光学工程， 2023， 硕士

【摘要】 钒元素自被发现以来,其氧化物的相变特性得到了人们的大量研究。其中,VO₂以最接近室温的相变温度受到了更多的关注。VO₂的相变可以通过热、电、光、压力等激励方式进行触发,其中电致相变的触发方式为VO₂的器件化应用提供便利。近年来,神经形态计算为解决冯·诺依曼瓶颈提供新的策略,用于神经形态计算的新型器件也成为一大研究热点。VO₂的电致相变特性为研制高性能莫特忆阻器神经元提供新机遇。具有大开关比、负微分电阻（Negative Differential Resistance,NDR）特性的VO₂薄膜是研制莫特忆阻器神经元的基础。目前,满足要求的VO₂薄膜大多通过高温外延工艺制备,这使VO₂莫特忆阻器的制备难以与传统的CMOS工艺兼容。本文以快速退火工艺制备了具有大开关比、NDR特性的VO₂忆阻器,并采用一个晶体管和一个电阻器（1-Transistor-1-Resistor,1T1R）结构制备了具有良好振荡特性的VO₂压控振荡器。在此基础上初步探索了薄膜厚度和环境温度对振荡器稳定性的影响,以及振荡器充当神经元的译码功能。本文主要研究如下:（1）研究了磁控溅射沉积非晶氧化钒薄膜后,两种不同方式获得的VO₂忆阻器。原位退火工艺制备的VO₂忆阻器的开关比低,且没有NDR区域,无法满足需求。第二种方式先进行快速退火,再利用电形成工艺将电极两端形成VO₂薄膜。快速退火工艺制备的VO₂忆阻器拥有两个数量级的开关比和明显的NDR区域,为后续振荡器的制备奠定基础。（2）研究了采用1T1R结构的VO₂压控振荡器的工作原理和频率性能。1T1R结构的VO₂振荡器单元中,VO₂莫特忆阻器作为电阻R,场效应管作为晶体管T。振荡电路中,VO₂忆阻器在负微分区域内提供负反馈功能,场效应管起限流分压作用。相比其它结构的VO₂振荡器,这种结构具有宽工作电压,振幅稳定,波峰可调等优点。400nm薄膜厚度的VO₂压控振荡器的中心频率为1.372MHz,可调比例±44%。（3）研究了薄膜厚度和环境温度对VO₂振荡器稳定性的影响,探索了该振荡器在神经形态计算中的应用。适当降低膜厚能有效提升振荡器中心频率,可调比例基本不变。VO₂振荡器对编码的时空信息进行解码,以清晰的波形展现。进一步说明该振荡器的仿生特性。更多还原

【Abstract】 Since vanadium was discovered,the phase transition characteristics of its oxides have been studied extensively.Among them,VO₂ has attracted more attention with its phase transition temperature closest to room temperature.The phase transition of VO₂can be triggered by thermal,electrical,optical,pressure and other excitation modes,among which the triggering mode of the electric phase transition provides convenience for the device application of VO₂.In recent years,neuromorphic computing provides a new strategy to solve Von Neumann’s bottleneck,and new devices for neuromorphic computing have become a hot research topic.The phase transformation characteristics of VO₂ provide a new opportunity for the development of high performance Mott memristor neurons.VO₂ thin films with high switching ratio and Negative Differential Resistance（NDR）are the basis for the development of Mott memristor neurons.At present,most of the VO₂ films that meet the requirements are prepared by high temperature epitaxy process,which makes the preparation of VO₂ Mott memrisor difficult to be compatible with the traditional CMOS process.In this thesis,a VO₂ memristor with large switching ratio and NDR characteristics was fabricated by rapid thermal annealing process,and a VO₂ VCO with good oscillation characteristics was fabricated by 1T1R structure.On this basis,the effects of film thickness and ambient temperature on the stability of the oscillator and the decoding function of the oscillator as a neuron are explored.The main research of this thesis is as follows:（1）The VO₂ memristor obtained by magnetron sputtering after deposition of amorphous vanadium oxide films is studied.The VO₂ memristor prepared by in situ annealing process has low switching ratio and no NDR region,so it cannot meet the demand.In the second way,rapid thermal annealing is carried out first,and VO₂ thin films are formed at both ends of the electrode by electroforming process.The VO₂memristor prepared by rapid thermal annealing process has two orders of magnitude switch ratio and distinct NDR region,which lays a foundation for the preparation of subsequent oscillators.（2）The working principle and frequency performance of VO₂ VCO with 1T1R structure are studied.In the VO₂ oscillator unit with 1T1R structure,the VO₂ Mott memristor is used as the resistor R,and the field effect transistor is used as the transistor T.In the oscillating circuit,the VO₂ memristor provides negative feedback function in the negative differential region,and the field effect transistor plays the role of current limiting and pressure dividing.Compared with other VO₂ oscillators,this structure has the advantages of wide operating voltage,stable amplitude,adjustable crest and so on.The VO₂ VCO with a 400nm film thickness has a center frequency of 1.372MHz and an adjustable ratio of±44%.（3）The influence of film thickness and ambient temperature on the stability of VO₂oscillator is studied,and the application of the oscillator in neural morphology calculation is explored.Appropriate reduction of film thickness can effectively improve the oscillator center frequency,adjustable ratio basically unchanged.The VO₂ oscillator decodes the encoded space-time information and presents it as a clear waveform.The bionic properties of the oscillator are further explained.更多还原