The normal incidence x-ray standing wave (NIXSW) technique is the primary source of quantitative experimental information on the adsorption height of many near-planar molecules on metal surfaces, of relevance to organic electronics. The technique yields two structural parameters, the coherent position and the coherent fraction. For high values of the coherent fraction the coherent position can be related directly to the adsorption height, but because the coherent fraction is effectively an order parameter, low values of this parameter are often attributed to partial disorder. It is certainly true that in depositing these large molecules on a surface it is very challenging to produce a perfectly ordered surface. However, is the type of disorder that is likely to occur able to account for no other effect on measured NIXSW data than a lowering of the coherent fraction? Here we show, by considering a wide range of possible types of ‘disorder’, that in almost all such situations it is improbable that the coherent positions associated with very low coherent fractions actually provide a reliable measure of the adsorption height of the ordered component, as is often assumed to be the case. As such, presentations of NIXSW data that only consider coherent position values are likely to be extremely misleading, and provide an unreliable benchmark for detailed understanding of these interfaces.

法向入射X射线驻波（NIXSW）技术是定量实验信息的主要来源，该信息是有关许多与有机电子相关的金属表面上许多近平面分子的吸附高度的信息。该技术产生两个结构参数，相干位置和相干分数。对于相干分数的高值，相干位置可以直接与吸附高度相关，但是由于相干分数实际上是有序参数，因此该参数的低值通常归因于部分无序。的确，要在表面上沉积这些大分子，要产生完美有序的表面是非常困难的。然而，除了降低相干分数之外，可能发生的疾病类型是否能够对测量的NIXSW数据没有其他影响？在这里，我们表明，通过考虑各种可能的“紊乱”类型，几乎在所有此类情况下，与非常低的相干馏分相关的相干位置实际上都无法提供有序组分吸附高度的可靠量度是不可能的，通常认为是这种情况。这样，仅考虑相干位置值的NIXSW数据的呈现可能会极具误导性，并且为详细理解这些接口提供了不可靠的基准。在几乎所有这样的情况下，与通常非常假定的情况一样，与非常低的相干部分相关的相干位置实际上不能提供有序组分吸附高度的可靠度量是不可能的。这样，仅考虑相干位置值的NIXSW数据的呈现可能会极具误导性，并且为详细理解这些接口提供了不可靠的基准。在几乎所有这样的情况下，与通常非常假定的情况一样，与非常低的相干部分相关的相干位置实际上不能提供有序组分吸附高度的可靠度量是不可能的。这样，仅考虑相干位置值的NIXSW数据的呈现可能会极具误导性，并且为详细理解这些接口提供了不可靠的基准。