CAJ | 학술논문

采用密度泛函理论的第一性原理方法研究了W(110) p(1×1)表面的STM图像对于衬底偏压的依赖性.计算结果表明:在衬底负偏压条件下,W(110) p(1×1)表面的钨原子在STM图像中显示为暗点而非通常在其它过渡金属中观察到的亮斑,并且暗点随偏压绝对值的减小而逐渐弱化.计算还模拟了恒流模式的STM测量时针尖的起伏变化.当衬底偏压在0～100 meV区间时,针尖起伏高度最为明显(～0.006 nm).在更高的正偏压下,STM的针尖起伏随偏压改变而线性变化(0.001 5～0.003 5 nm).这些结果说明了W(110) p(1×1)表面是非常平坦的.由于钨原子的价电子为5d态,和3d电子相比具有更为扩展的行为,表面态电子波函数交叠区间集中在原子周围,所以STM测量时亮点突起出现在原子的周围.
채용밀도범함이론적제일성원리방법연구료W(110) p(1×1)표면적STM도상대우츤저편압적의뢰성.계산결과표명:재츤저부편압조건하,W(110) p(1×1)표면적오원자재STM도상중현시위암점이비통상재기타과도금속중관찰도적량반,병차암점수편압절대치적감소이축점약화.계산환모의료항류모식적STM측량시침첨적기복변화.당츤저편압재0～100 meV구간시,침첨기복고도최위명현(～0.006 nm).재경고적정편압하,STM적침첨기복수편압개변이선성변화(0.001 5～0.003 5 nm).저사결과설명료W(110) p(1×1)표면시비상평탄적.유우오원자적개전자위5d태,화3d전자상비구유경위확전적행위,표면태전자파함수교첩구간집중재원자주위,소이STM측량시량점돌기출현재원자적주위.
The dependence of STM images on bias voltage for reconstructed W(110) p(1×1) surface was investigated by using the density-functional theory calculations. The calculated results showed that in negative bias voltage region the positions over the surface atoms are dark while the empty hollow sites are bright and the darkness of atom positions are smoothed when decreasing bias voltages. In constant-current mode, the topography of the STM images with several voltages was simulated in the same approach. The simulated STM tip corrugations were also presented in details: the maximum corrugation (～0.006 nm) appeared within 0-100 meV and in higher positive bias voltages the corrugation varies linearly in the range of 0.001 5-0.003 5 nm. These observations indicated that the W(110) p(1×1) surface is almost flat even there exists the hollow sites in the sense of STM experiment. Since the 5d states of tungsten are more extended than that of 3d electrons, the overlap of surface electron wave function mainly occurs normally between neighboring atoms, which may explain why bright spots appear around the atomic sites in STM images of W(110) p(1×1).